As a conjunction meaning "but" or "however":
When "でも" is used as a conjunction, it typically conveys a meaning similar to "but" or "however" in English.
In this role, it's used to indicate a contrast or opposition, similar to how "but" or "however" is used in English. Essentially, you can use "でも" when the statement in the preceding sentence and the following sentence depict contrasting ideas or situations.
Examples Sentences
Japanese
明日はテストだ。でも全然勉強していない。
English
I have a test tomorrow. But, I haven't studied at all.
Japanese
この料理はおいしい。でもちょっと辛すぎるかも。
English
This dish is delicious. But, it might be a bit too spicy.
Japanese
彼は忙しい。でもいつも手伝ってくれる。
English
He is busy. However, he always helps out.
In my opinion, when "でも" is used in the sense of "but," it often gives off a somewhat casual impression.
While it's not strictly off-limits in business settings, it's advisable to use "でも" thoughtfully, taking into consideration the other party's style and the context of your conversation.
Informal or Formal
Informal
Formal
Spoken or Written language
Spoken
Written
※ My personal impressions are quantified and may vary from person to person.
As a particle for suggestion with "でも"
When "でも" attaches to the dictionary form of a verb, in the form of "~ても", it is used for suggestions, similar to "how about" or "what if" in English.
Japanese
映画でもどうですか?
English
How about watching a movie?
Japanese
食事でもどうですか?
English
How about going for a meal together?
Informal or Formal
Informal
Formal
Spoken or Written language
Spoken
Written
※ My personal impressions are quantified and may vary from person to person.