These are three alternatives which all have the same meaning: 1. I shower 2. I take a shower 3. I have a shower In the first sentence 'shower' is a verb. In the other two sentences, the word 'shower' is a noun: it's a singular, countable noun so it needs the article 'a'. Generally speaking, where two forms exist, collocations with 'take' are more common in American English, while collocations with 'have' are more common in British English.

I have a shower (more common in Britain). I take a shower (more common in the U.S.). Both forms are used in both countries. I shower is correct but less common in informal speech.

Only “I shower” is correct. “I take shower” is wrong. You would have to say “I take showers” or “I take a shower” “I have shower” is wrong. “I have showered” or “I have a shower”. There are many ways to say it. I would need to know the complete sentence to give you better advice.