How do we figure out which lexical class (part of speech) a word belongs to if we look at

1. several things?
2. What was a constituent of a species?
3. Does a word have a modifier, modifier or complement?
4. Why is this word morphologically unmarked as belonging to a specific class?

What does it mean for a word to be a verb? What if we wouldn’t define it as something? The shape we use of words or words comes from categories.

In this case, the word appears to belong to a noun phrase.

1. A while is the complement of the preposition for while which often takes noun phrases as complements.
2. A while has similar shape to a noun phrase, with determiner ( a ), and head ( while ). Adverbs take a different form of determiners from adjective.
3. A while can also take adjectival, but not adverbial, modification: a long while but not *a quickly while.

What is the shape of a word? When you see a word ending in -ly you hunch it’s an adjective, especially if it’s a base adjective. Do you have a different story or who, why and why is it still true?

In English, word shape tends to be a less reliable indicator than many languages, but it’s still useful. For nouns, we want to focus on the inflections the word can take; while is rarely plural, you will occasionally hear native speakers say things like “just a few whiles ago”, so it’s not entirely out of the question, either. Inflecting like a noun is another strong suggestion that while is a noun.

In this case, all the evidence points pretty strongly to the direction of while being a noun.