A martyr is someone who is killed or made to suffer greatly because of their religious or political beliefs, and is admired and respected by people who share those beliefs.

If someone is martyred, they are killed or made to suffer greatly because of their religious or political beliefs.

If you refer to someone as a martyr, you disapprove of the fact that they pretend to suffer, or exaggerate their suffering, in order to get sympathy or praise from other people.

If you say that someone is a martyr to something, you mean that they suffer as a result of it.