It's hard to figure out what "it" is in your question. Are you referring to the subject of a sentence that has two nouns connected by the word and, as in Bob and Ray are playing baseball? In that case, the subject, Bob and Ray, is plural and takes a plural verb. But when the two nouns connected by and act as a unit, they take a singular verb, as in Ham and eggs is my favorite breakfast and Pork and beans tastes great.
it is the first sentence and states part of the question
It is a grammatical unit of one or more words that expresses a statement, opinion or decision
How to use the word in a sentence.
we don't know what you are talking about.
The joule is the unit of energy in the International System of Units.
No it should not, unless it is at the start of a sentence.
Did you know that the chloroplast is part of a plant cell which contains chlorophyll.
the square unit of....!
"Month" is a noun in that sentence, and just now, I can't think ofa case where that word is used as any other part of speech.
In this kind of sentence, "how" is usually considered an adverb, modifying the verb infinitive "to write".
The term for knowing a word's part of speech in order to appropriately use it in a sentence is "word-usage."
i only know 3 gaudy, gla, and heed