In Vowels^x, Singular nouns^x

Yes I am little confuse now in between articles. Mr. Wordy what if i used sheet and mattress for the 1st time. Article A won't look like repeating or odd ?Its wooden frame supports a bouncy mattress and is completely covered with a silky sheet like a sponge cake layered with cream.And some...

A and an signal that the noun modified is indefinite, referring to any member of a group. These indefinite articles are used with singular nouns when the noun is general; the corresponding indefinite quantity word some is used for plural general nouns. The rule is: a + singular noun...