stylistic:tone, information:extraction
Pronoun versus pro-form

Pronoun is a category of words. A pro-form is a type of function word or expression that stands in for (expresses the same content as) another word, phrase, clause or sentence where the meaning is recoverable from the context. In English, pronouns mostly function as pro-forms, but there are pronouns that are not pro-forms and pro-forms that are not pronouns.

Examples are pronouns and pro-forms. In, the pronoun it "stands in" for whatever was mentioned and is a good idea. In, the relative pronoun who stands in for "the people".

Examples are pronouns but not pro-forms. In, the interrogative pronoun who does not stand in for anything. Similarly, in, it is a dummy pronoun, one that does not stand in for anything. No other word can function there with the same meaning; we do not say "the sky is raining" or "the weather is raining".

A prop-word is a word with little or no semantic content used where grammar dictates a certain sentence member, e.g., to provide a "support" on which to hang a modifier. The word most commonly considered as a prop-word in English is one (with the plural form ones). The prop-word one takes the place of a countable noun in a noun phrase (or determiner phrase), normally in a context where it is clear which noun it is replacing. For example, in a context in which hats are being talked about, the red one means "the red hat", and the ones we bought means "the hats we bought". The prop-word thus functions somewhat similarly to a pronoun, except that a pronoun usually takes the place of a whole noun (determiner) phrase (for example, "the red hat" may be replaced by the pronoun "it".)

Finally, in, there are pro-forms that are not pronouns. In, did so is a verb phrase that stands in for "helped", inflected from to help stated earlier in the sentence. Similarly, in, others is a common noun, not a pronoun, but the others probably stands in for the names of other people involved (e.g., Sho, Alana, and Ali), all proper nouns.