What are the different ways of saying to agree or disagree with a person?

Question

There seems to be many different ways of saying either to agree or to disagree with a person.

Which words are there, in what circumstances should they be used, and are there any relevant examples of their usage?

One example is I'd like to be able to say "It's OK if you don't agree with me" but I don't know how to.

(This is a spinoff question as I thought the original was getting too broad. For finer points and examples on using に同意する to agree/disagree with a person, see also How to use ～に同意する to agree or disagree with a person?)

Answer 1

"＊" indicates any one of the particles に／が／は／で／には／と／を to save space.

Words which mean "agree" (or "disagree" if in negative tense):

• ～に同意{どうい}する - Means to have the same opinion with somebody/something, or to agree to something.
• （～に）同感{どうかん} - A "softer" form of に同意{どうい}する which is used to indicate sympathy or having the same feeling about somebody/something. Often used just by itself (e.g. 同感{どうかん}！ "I agree!".)
  Is sometimes used with する but is more commonly ended with a copula, for example 彼{かれ}に同感{どうかん}だ。
• ～に賛成{さんせい}する - Means "to approve", often used when supporting or endorsing a plan or proposal.
• ～に賛同{さんどう}する - Has a similar meaning to ～に賛成{さんせい}する.
• ～＊納得{なっとく}する - Indicates assent or consent.
• ～＊納得{なっとく}できる／～＊納得{なっとく}（が）いく - Indicates acceptance or being satisfied. The negative forms can mean "I'm not convinced" or "I'm not satisfied". 納得{なっとく}いかない！ for instance means "I can't stand this!"
• ～と意見{いけん}が合{あ}う - Used to express agreement with another person's idea or what they're saying.

Words which mean "disagree":

• ～と意見{いけん}が異{こと}なる - To differ in opinions or be in disagreement with.
• ～（に）異論{いろん}がある - A slightly formal form of expressing having a different view with someone.
• ～と食{く}い違{ちが}う - A strong form of disagreement, meaning clash or differ with.

Note: する/しない is often replaced with できる/できない to say either I can/can't agree with something.