Context-based Parts of Speech

Words are divided into different classes according to the work they do in sentences.

• Some words always do only one work.

E.g. Believe and destroy can only be verbs. Independence can only be a noun.

• But some words do different work depending on their use in the sentence.

We cannot say to which part of speech such a word belongs unless we see it used in a sentence.

Mragank has been chosen for the school play. (Noun)
Federer and Nadal play tennis together on Saturdays. (Verb)

We ate in the afternoon. (Noun)
We had afternoon tea. (Adjective)

They arrived soon after. (Adverb)
They arrived after us. (Preposition)
They arrived after we had left. (Conjunction)

Are you well? (Adjective)
She speaks well. (Adverb)
Well! That’s expensive! (Interjection)

I am staying in this evening. (in - adverb)
Look in the big box. (in – preposition)

So, Parts of speech is context based. You cannot memorize the words as belonging to one or the other part of speech. You will have to look at the sentence and find out what work a word is performing in that sentence.