A – An – Some
A and an can only be used with nouns in the singular if we don't mean a special thing or person. Some can only be used in the plural if we don't know the exact amount of something or if we use nous we can not count, e.g. liquids.
Singular: a or an
|a banana||a car||a monkey||a football|
|an egg||an accident||an umbrella||an eagle|
Do you have a ball? - not a special ball
She doesn't have a sister. - not a special sister
Plural: some with countable nouns
|some bananas||some cats||some monkeys||some balls|
|some eggs||some oranges||some umbrellas||some eagles|
Buy some tomatoes, please. - not a special amount
They have some children, haven't they? - we don't know how many
Use some for things you can't count
|some milk||some water||some coffee||some sugar|
|some tea||some juice||some money||some butter|
Would you like some orange juice? - May I have some more honey?
We can't count juice or honey - only glasses, litre, tins, kilos, ...