Learn Hardcore Russian: Он говорит тише, чем обычно.

Russian normally does not distinguish between simple present and present continuous the way English does. Context tells you whether it’s about a current action or a general tendency.

What is тише? Is it an adjective or an adverb, and what is the base form?

Тише is the comparative form of the adverb тихо (quietly).

Base adverb: тихо = quietly
Comparative adverb: тише = more quietly

It is historically related to the adjective тихий (quiet), but in this sentence тише is functioning as an adverb describing how he speaks.

Why is it тише and not something like более тихо for “more quietly”?

Russian has many short, synthetic comparative forms like тише, громче, лучше, хуже, etc. These are the normal, natural way to compare.

You can say более тихо, and it’s grammatically correct, but here it sounds more bookish or unnatural in everyday speech. Он говорит тише is the default, idiomatic choice.

What is the role of чем in тише, чем обычно? Is it like English “than”?

Yes. Чем here means than in a comparison:

тише, чем обычно = more quietly than usual

This is the standard way to build a comparison:
comparative + чем + what you compare with
e.g. быстрее, чем вчера (faster than yesterday), громче, чем он (louder than him).

Is чем always required after a comparative, or can it be omitted?

Often you do use чем, but there are alternatives:

With чем (most common and clear):
- Он говорит тише, чем обычно.
With a genitive form (no чем):
- Он говорит тише обычного.
  Here обычного is genitive singular of обычный used as a noun-like word meaning “the usual (way)”.

Both are correct. With обычно, specifically as an adverb, you need чем:

тише, чем обычно (you cannot say *тише обычно).

What part of speech is обычно, and how is it related to обычный?

Обычно is an adverb meaning usually / normally.

It comes from the adjective обычный (usual, ordinary):

обычный (adj.) → обычно (adv.)

In this sentence it stays in one form (no case, no gender):
чем обычно = than (it is) usually / than usual.

Can I change the word order, for example Он тише говорит, чем обычно?

Yes, that word order is possible:

Он говорит тише, чем обычно. (most neutral)
Он тише говорит, чем обычно. (slight emphasis on тише, “he more quietly SPEAKS than usual”)

Russian word order is relatively flexible, but subject–verb–adverb–чем-phrase is the most typical pattern for learners to stick to. The meaning is essentially the same.

How would I say the same idea in the past or future?

Change говорит to the appropriate tense, keep the rest:

Past: Он говорил тише, чем обычно.
→ He spoke / was speaking more quietly than usual.
Future (simple future of сказать isn’t used here; you use будет говорить):
Он будет говорить тише, чем обычно.
→ He will speak / will be speaking more quietly than usual.

Can I drop говорит and just say Он тише, чем обычно?

Yes, in context you can say:

Он тише, чем обычно.

Literally that’s “He is quieter than usual.” It describes him as being quieter in general (maybe he’s less talkative, more silent).

Your original sentence Он говорит тише, чем обычно focuses specifically on how he is speaking, not on his overall behavior or personality.

Is there any difference between говорит and разговаривает in a sentence like this?

Both are related to speaking, but they differ slightly:

говорит = “speaks / is speaking / says” (neutral verb of speaking)
разговаривает = “is talking / is having a conversation”

You could say:
Он разговаривает тише, чем обычно.
This would stress that he is talking with someone more quietly than usual, while говорит can be more general (speaking, saying something, giving a speech, etc.).