I am trying to understand when plain conjugations should be used in polite
speech. My basic understanding is that plain conjugations are always used when
they are followed by particular particles, typically when they appear in the
middle of phrases, or when they express actions that are themselves objects of
a sentence. For example:

> 何かを見たと言っています

(`見た` is in plain form)

or

> それは言うのが難しいです

(`言う` is in plain form)

Is there a rule of thumb to keep in mind when deciding whether the form of
verbs should be used in polite speech? It is okay if there is not a surefire
answer – any advice would be helpful!
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2021-09-02T23:44:18.340
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2021-09-03T00:54:08.610
2021-09-03T00:54:08.610
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question
grammar conjugations
Circumstances where polite form is never used?