Learn English – A sentence may contain two nouns back-to-back. How are these nouns written

A sentence may contain two nouns back-to-back. How are these nouns written together?

I went to that book store.
I went to that bookstore.
I went to that book-store.

Why can these two nouns be adjacent to each other without being combined or without added punctuation?

balloon sleeves

Is it acceptable to write the two nouns like either of the following? Why or why not?

balloon-sleeves
balloonsleeves

But what about this:

”. . .I am opening the flood-gates myself. . .”?

Which is grammatically correct?

flood-gates
floodgates

Does the correct manner in which "flood gates" is written apply to all pairs of adjacent nouns?

Best Answer

The general rule for noun phrases like this is to separate them by spaces.

However, many* specific pairs of words have exceptions and are either written hyphenated, or are even merged into a new word with no separation at all. For example, "copy editor" is in the process of moving from unhyphenated noun phrase through hyphenated noun phrase to new word, although at present all three forms are more or less acceptable.

Your specific examples are customarily written like this:

"bookstore" (although "book store" is acceptable; "book-store" looks odd, as though you had realized it was a very common phrase but hadn't realized it was so common it was its own word already)
"balloon sleeves" (and only that way: it's just not very common)
"floodgates" (it's been a single word for centuries, so even "flood gates" seems a bit off)

_{*Very many. Seriously, there are a lot. Noun phrase collocations are quite common.}