Radius of observable universe (correction) | Cosmology & Astronomy | Khan Academy
A1 A2 B1 B2 C1 C2
big
US / bɪɡ /
•UK / bɪɡ /
- adjecitve
- Popular
- Serious
- Large
little
US / 'lɪtl /
•UK / ˈlɪtl /
- adjecitve
- Being short in length of time
- Not great in size, amount, or degree; small
- Being very young or younger than others
- adverb
- By an amount or degree that is not very much
- Not often; rarely
- noun
- A person's name
the
US / ðə /
•UK / ðə /
- article
- Used to refer to something already mentioned
- Used to show there is only one of something
- determiner
- Used to describe all of a family
this
US / ðɪs /
•UK / ðɪs /
- adjecitve
- Used to indicate something already been discussed
- Used to indicate something happening around now
- adverb
- An indication by a physical motion or gesture
- A specific amount of
- determiner
- Person, thing, or idea near you
- pronoun
- Person, thing that has already been discussed
kind
US / kaɪnd /
•UK / kaɪnd /
- adjecitve
- In a caring and helpful manner
- friendly and considerate
- noun
- One type of thing
year
US / jə: /
•UK / jɪr /
- noun
- Unit of time equal to 12 months or 365 or 366 days
- Used to refer to the age of a person
you
US / jʊ /
•UK / ju /
- pronoun
- Person someone is speaking or writing to
- Person or people in general
make
US / meɪk /
•UK / mek /
- noun
- Product made by a particular company; brand
- verb
- To arrange or prepare something e.g. dinner
- To get to (a place) on time
- To gain the status of (teacher, lawyer, etc.)
- To create something by putting things together
- To earn a certain amount of money at a job
- To cause or force a person to do something
- To cause something to happen or be formed
universe
US / ˈju:nɪvɜ:s /
•UK / ˈjunəˌvɚs /
- noun
- All of space that contains planets and stars
- Things surrounding a person, affecting their life
where
US / hwɛə /
•UK / hwɛr, wɛr /
- conjunction
- At or in the place which
- In whatever place
- pronoun
- Word you use to ask the location of something
leave
US / li:v /
•UK / liv /
- noun
- Permission to do something
- Vacation time; time off work
- verb
- To go away from; depart
- To gift property to someone after you die
- To allow something to continue happening
- To let something remain unused or available
- To let something or someone remain somewhere
approximately
US / əˈprɒksɪmətli /
•UK / əˈprɑksəmɪtlɪ /
- adverb
- Around; nearly; almost; about (a number)
something
US / ˈsʌmθɪŋ /
•UK / ˈsʌmθɪŋ /
- adverb
- In some degree or measure
- noun
- a person or thing of some value or consequence
- pronoun
- Thing that is not yet known or named
- Approximately
keep
US / ki:p /
•UK / kip /
- noun
- Large, strong tower in the middle of a castle
- Money spent on you so you can live in a place
- verb
- To continue doing something; not to stop
- To stop balls going in a goal in sports
- To not give back or return something
- (Of food) to not spoil or not rot
- To take possession of something to own, e.g. a pet
- To have and continue to hold something
- To do something that you have promised or agreed
- To stay in a certain place or condition
- To maintain the rules
over
US / 'əʊvə(r) /
•UK / ˈovɚ /
- adverb
- Finished; no longer happening
- Towards the ground/away from a standing position
- noun
- A set of six consecutive balls bowled in cricket
- other
- Finished
- preposition
- Showing the relation when a thing is above another
- On or covering something
- Above or across something
- More than you need
- From one side to the other
- In the direction of; toward
from
US / frəm /
•UK / frʌm, frɑm,frəm /
- preposition
- Starting at a particular place, time or level
only
US / ˈəunli /
•UK / ˈonli /
- adverb
- Just one; just that amount or thing; not more than
- Not very important or serious
- Just that type of thing, person
- Short time ago; not before a certain time
- conjunction
- Except; but
photon
US / ˈfəʊtɒn /
•UK / ˈfoʊtɑ:n /
- noun
- Particle with energy but no mass, electric charge
affect
US / ə'fekt /
•UK / əˈfɛkt /
- verb
- To cause a change in something else
hopefully
US / ˈhəʊpfəli /
•UK / ˈhopfəli /
- adverb
- In a manner wishing something to happen
and
US / ənd /
•UK / ənd, ən,ænd /
- conjunction
- Used to refer to two or more things
- Plus; in addition; on top of that
- Used to introduce an action that follows another
hey
US / heɪ /
•UK / he /
- exclamation
- What you say when you want someone's attention
think
US / θɪŋk /
•UK / θɪŋk /
- verb
- To have an idea about something without certainty
- To have an idea, opinion or belief about something
precision
US / prɪˈsɪʒn /
•UK / prɪˈsɪʒən /
- adjecitve
- Performed in a very careful, detailed manner
- noun
- Quality of being very accurate and exact
affair
US / ə'feə(r) /
•UK / əˈfɛr /
- noun
- Secret sexual relationship between two people
- Event or a set of events, often unpleasant ones
away
US / ə'weɪ /
•UK / əˈwe /
- adjecitve
- Not present
- adverb
- Disappear completely
- Doing something with a lot of energy
- Not here; far from here; in a different direction
- To a different area, location
clear
US / klɪə(r) /
•UK / klɪr /
- adjecitve
- Empty; without anything in it or on it
- Being certain and without doubt
- Being without any streaks, spots, or cracks
- Easy to understand; well-explained; obvious
- adverb
- Completely; entirely; through the whole of
- Away from; free from
- verb
- To recover from or remove a problem
- To get rid of the entire contents of
- To give permission for something to happen
- To make a place or surface empty by removing
- To prove that someone is not guilty or to blame
have
US / həv /
•UK / hæv /
- verb
- To drink, smoke, eat or use something
- To experience the effects of something
- To organize an event, or join in an activity
- To own, possess, or hold something
- To cause to happen or produce a particular effect
last
US / lɑ:st /
•UK / læst /
- adjecitve
- Most recent; the latest
- The one before
- adverb
- Final; with nothing following; after all others
- Most recent; the latest
- determiner
- The one at the end
- verb
- To remain or continue for a certain period of time
many
US / 'menɪ /
•UK / ˈmɛni /
- determiner
- Used to refer a large number of things
after
US / 'ɑ:ftə(r) /
•UK / ˈæftɚ /
- adverb
- Later than another time, or behind something
- conjunction
- Following something before
- preposition
- When an event happened or time has passed
actually
US / ˈæktʃuəli /
•UK / ˈæktʃuəli /
- adverb
- Used to add new (often different) information
should
US / ʃʊd /
•UK / ʃʊd /
- other
- Used to indicate what is proper or reasonable
obviously
US / ˈɒbviəsli /
•UK / ˈɑːbviəsli /
- adverb
- In a way that is obvious/easy to see or understand
million
US / ˈmɪljən /
•UK / ˈmɪljən /
- number
- 1,000,000
sure
US / ʃʊə(r) /
•UK / ʃʊr /
- adjecitve
- Having no doubts about something
- Have confidence in your own words or actions
- Firmly established or held; being firm or stable
- Being correct or true
- adverb
- What you say to agree willingly
point
US / pɔɪnt /
•UK / pɔɪnt /
- noun
- An item to be discussed
- Small spot or dot
- Fact or detail
- Feature of something
- The size of the text on a page or screen
- A certain time or stage in a process
- Certain position in time or space
- Idea or fact you try to convince people about
- Measurement of scores in a game, sport
- Sharp end of something, e.g. a pen or pin
- verb
- To face a certain direction, e.g. north
- To indicate something with your finger to others
quick
US / kwɪk /
•UK / kwɪk /
- adjecitve
- Using very little time; moving far in little time
- Learning and understanding rapidly and easily
here
US / hɪə(r) /
•UK / hɪr /
- adverb
- In this place; at this location, position or time
too
US / tu: /
•UK / tu /
- adverb
- In addition, also; with emphasis
- Say that something is more than you want
number
US / ˈnʌmbə(r) /
•UK / ˈnʌmbɚ /
- noun
- Symbols such as 1, 2, 56, 793
- Particular song or dance performed during a show
- Total quantity or amount of things
- verb
- To put numbers on things
- To assign a sequence within a group, series, set
- To claim to be part of a larger group, series, set
enough
US / ɪˈnʌf /
•UK / ɪˈnʌf /
- adjecitve
- Sufficient to answer the need
- adverb
- To a satisfactory degree
- pronoun
- Equal to what is needed; as much as required
- Adequate number or amount
expand
US / ɪk'spænd /
•UK / ɪkˈspænd /
- verb
- To make something larger in size, number, amount
bang
US / bæŋ /
•UK / bæŋ /
- noun
- Sudden loud noise, as when a bomb explodes
- A loud noise
- verb
- To strike something loudly or forcefully
that
US / ðæt /
•UK / ðæt, ðət /
- adjecitve
- The person or thing being talked about
- Used to identify something both the speakers know
- adverb
- Used to reinforce adjectives and adverbs
- To such a degree
- conjunction
- Used to connect a noun clause
- Used to introduce an adverbial clause
- Used to introduce a noun clause
- determiner
- Used as a noun to refer to something
- pronoun
- Referring an object far away
- Used to refer to the relative pronoun ‘which’
what
US / wɒt /
•UK / hwɑt, hwʌt, wɔt, wʌt,hwət, wət /
- pronoun
- Thing or things that; the same kind as
- Used to emphasize something you are about to say
- adjecitve
- Used to refer to a particular amount, or number
- Used to place emphasis on a particular quality
- adverb
- To a certain degree
- determiner
- Question words used for asking for information
- exclamation
- Used to express excitement, shock, or surprise
- Used to ask people to repeat something they said
even
US / 'i:vn /
•UK / ˈivən /
- adjecitve
- Being equal in influence, power, possibility etc.
- Being divided equally or fairly
- (Of teams/contest) with similar chances of success
- Smooth, level, or regular
- Can be divided by 2; ending in 2, 4, 6, 8, or 0
- At a regular, equally steady manner
- Remaining steady and unchanging
- adverb
- (When this is surprising) as well; too
- (Used to compare two things/stress the difference)
- verb
- To make something level; to flatten
- To make something equal
current
US / 'kʌrənt /
•UK / ˈkɚrənt, ˈkʌr- /
- adjecitve
- Happening or being in the present time
- noun
- Electricity flowing through wires
- Movement of water in a river, or air in the sky
about
US / ə'baʊt /
•UK / əˈbaʊt /
- adverb
- To be ready to; going to
- Nearly; approximately; roughly
- Near; next to; close to
- In every direction; in the area of
- preposition
- Concerning or of (a topic)
right
US / raɪt /
•UK / raɪt /
- adjecitve
- Correct or true
- The south side of you looking at the rising sun
- adverb
- Exactly in a place or time
- Being appropriate for a particular event
- In a straight or direct manner
- noun
- Something you are legally or morally allowed to do
- Ideal of what is just and good
- Political view based on conservatism
- verb
- To fix something previously wrong or unjust
- To make upright, as a boat that has turned over
observable
US / əbˈzɜ:vəbl /
•UK / əbˈzɚvəbəl /
- adjecitve
- Being able to be seen, noticed, or sensed
happen
US / 'hæpən /
•UK / ˈhæpən /
- verb
- To take place or occur
incorrectly
US / ˌɪnkə'rektlɪ /
•UK / ˌɪnkə'rektlɪ /
- adverb
- In a way that is incorrect or wrong
understanding
US / ˌʌndəˈstændɪŋ /
•UK / ˌʌndərˈstændɪŋ /
- adjecitve
- Being sympathetic
- noun
- When you get the meaning correctly; comprehension
- Knowledge about something or someone
- verb
- To know the meaning of language, what someone says
place
US / pleɪs /
•UK / ples /
- noun
- Particular location, area or region
- verb
- To put someone in a particular type of situation
- To put something in a certain location or position
then
US / ðen /
•UK / ðɛn /
- adverb
- A time that is not now
- Following another thing in time or arrangement
- Following on reasonably from what was just stated
- At that time, not now
hard
US / hɑ:d /
•UK / hɑː(r)d /
- adjecitve
- Difficult to do; difficult to understand
- (Of facts) not able to be misunderstood; clear
- (Of alcohol) strong
- Involving or requiring lots of work, effort, care
- Being full of pain, trouble, and problems
- Strong
- (Of edge) clear; sharp
- Difficult to bend, break or cut; solid
- adverb
- With lots of force, power, or impact
get
US / ɡet /
•UK / ɡɛt /
- verb
- To become affected by illness or disease
- To begin to feel or understand an emotion or idea
- To send or bring someone or something home, etc.
- To go somewhere to obtain something
- To (cause to) do a particular thing
- To obtain, receive or be given something
- To currently have
- To prepare for use
- To understand something being said or read
video
US / 'vɪdɪəʊ /
•UK / ˈvɪdiˌo /
- adjecitve
- Of a moving film, with sound
- noun
- Recording capturing action with sound
- verb
- To make a moving film of, with sound
want
US / wɔnt /
•UK / wɑnt, wɔnt /
- noun
- Something you desire or wish for
- State or condition of poverty
- verb
- To desire or wish for something; hope for a thing
significant
US / sɪgˈnɪfɪkənt /
•UK / sɪɡˈnɪfɪkənt /
- adjecitve
- Large enough to be noticed or have an effect
- Having meaning; important; noticeable
- (Statistics) being clearly different
would
US / wʊd /
•UK / wʊd /
- other
- Used to indicate something imagined
- Used to ask or request something politely
- Verb used to indicate possibility, request etc.
- Used to indicate a preference
- Used to indicate a reaction
- Indicates something that occurred repeatedly
- Used to indicate willingness or ability to do
understand
US / ˌʌndə'stænd /
•UK / ˌʌndɚˈstænd /
- verb
- To know the meaning of language, what someone says
really
US / ˈri:əli /
•UK / ˈriəˌli, ˈrili /
- adverb
- Used to stress something that is said; definitely
- In a true or accurate manner
- Very
but
US / bət /
•UK / bʌt,bət /
- conjunction
- Used before you say something different, opposite
now
US / naʊ /
•UK / naʊ /
- adverb
- At the present time or moment
- Right away or in the next possible moment
- Used to refer to something that just happened
- Time between the present and a moment in the past
- conjunction
- Resulting from or because of something
maybe
US / ˈmeɪbi /
•UK / ˈmebi /
- adverb
- Possibly but not certainly; perhaps
our
US / 'aʊə(r) /
•UK / aʊr /
- determiner
- Belonging to us
not
US / nɒt /
•UK / nɑt /
- adverb
- Word indicating the negative
- (Used to form the negative of verbs)
digit
US / ˈdɪdʒɪt /
•UK / ˈdɪdʒɪt /
- noun
- Person's finger or toe
- Written symbol of the numbers from 0 to 9
bit
US / bɪt /
•UK / bɪt /
- noun
- Device put in a horse's mouth to control it
- Small piece of something
- verb
- (E.g. of fish) to take bait and be caught
error
US / ˈerə(r) /
•UK / ˈɛrɚ /
- noun
- Something that is not correct; a mistake
billion
US / ˈbɪljən /
•UK / ˈbɪljən /
- noun
- Number 1,000,000,000
travel
US / ˈtrævl /
•UK / ˈtrævəl /
- noun
- Going to other places, esp. distant places
- verb
- To go to a place that is far away
space
US / speɪs /
•UK / spes /
- noun
- Empty area kept for a specific reason, like a car
- Empty area with nothing in it
- Area in the sky where the stars are
- Area between written words on a page
- verb
- To make a certain distance or time between
change
US / tʃeɪndʒ /
•UK / tʃendʒ /
- noun
- Exchange of one set of clothes for another
- Money in the form of coins instead of paper
- Money returned after giving too much
- Act of making or becoming something else
- verb
- To exchange one set of clothes for another
- To exchange one kind of money for another
- To replace something with another thing
- To make or become something else
- To go from one train, bus, etc. and go to another
slight
US / slaɪt /
•UK / slaɪt /
- adjecitve
- Small (amount, quality)
- Appearing thin, delicate and physically weak
- noun
- Rude and disrepectful treatment
- verb
- To ignore or treat rudely and with no respect
take
US / teɪk /
•UK / tek /
- noun
- Filming of a single scene for TV or the movies
- verb
- To accept something that is offered
- To use a method of traveling, e.g. a bus or train
- To use a camera to make (a photo)
- To pick up something and go away with it
- To study a subject in school
- To attempt to pass (an exam)
- To require a certain amount of time, money, space
ago
US / əˈgəʊ /
•UK / əˈgoʊ /
- adverb
- At a specified length of time in the past
all
US / ɔ:l /
•UK / ɔl /
- adverb
- Completely; totally
- determiner
- Being every one of something
- pronoun
- 100% of something; the complete amount
correct
US / kə'rekt /
•UK / kəˈrɛkt /
- adjecitve
- Being suitable and appropriate for an occasion
- True or accurate
- verb
- To fix a problem
- To write marks on a piece of work to show mistakes
- To punish in order to improve
talk
US / tɔ:k /
•UK / tɔk /
- noun
- Style of speaking
- Discussion between two countries
- Giving information in front of people; lecture
- Saying things or ideas to someone with words
- verb
- To make a formal speech about something
- To say things or ideas to someone with words
just
US / dʒʌst /
•UK / dʒʌst /
- adjecitve
- Proper or appropriate; as is deserved
- Doing or being what is right or fair
- Legally correct; having enough evidence
- adverb
- Almost; nearly
- Exactly at the time of
- Exactly (the same as, like)
math
US / mæθ /
•UK / mæθ /
- noun
- Study or science of numbers and shapes
light
US / laɪt /
•UK / laɪt /
- adjecitve
- Being bright making it easy to see; not dark
- Being pale and lacking darkness of color
- Not heavy; weighing only a little
- adverb
- Carrying few bags when traveling
- noun
- A source of energy that makes a room or area bright
- Way in which something or someone is understood
- verb
- To cause something to burn; put a burning match to
- To provide a way to see ahead
much
US / mʌtʃ /
•UK / mʌtʃ /
- adjecitve
- Very; to a high level or degree
- adverb
- A lot; large amount; a high degree of
- Nearly; basically
- On many occasions; often
- noun
- A large amount; a great quantity
decimal
US / 'desɪml /
•UK / ˈdɛsəməl /
- noun
- Number using one equal tenth of a whole as a basis
traverse
US / trəˈvɜ:s /
•UK / trəˈvɜ:rs /
- verb
- To pass across, over, or through
start
US / stɑ:t /
•UK / stɑrt /
- noun
- First time or place that a thing exists; beginning
- First opportunity to achieve something, e.g. a job
- Sudden action or movement because you are scared
- other
- Beginning of something in place or time
- verb
- To do, be or happen for the first time; begin
- To turn something on
state
US / steɪt /
•UK / stet /
- adjecitve
- Concerning region within a country
- noun
- Region within a country, with its own government
- Situation or condition something is in
- verb
- To say; declare as fact
less
US / les /
•UK / lɛs /
- adjecitve
- Smaller in amount or degree
- adverb
- To a smaller degree
- noun
- A smaller amount
- preposition
- With the subtraction of
answer
US / 'ɑ:nsə(r) /
•UK / ˈænsɚ /
- noun
- Reply to a question someone asks
- Solution to a problem or test question
- verb
- To reply to a question someone asks
- To solve a test question or a problem
than
US / ðən /
•UK / ðən /
- conjunction
- Used to compare two things that are not equal