It’s not uncommon for evangelical Christians to say that Christianity is not a religion, it’s a relationship. Or to contrast works-based religion with faith-based Christianity, making that the difference between religion and non-religion.
But it’s a mistake to say that Christianity is not a religion. For one thing, that would mean religious freedom wouldn’t be important for Christians. But we dare not give up religious freedom. For another thing, it drops the question of which religion is true. And it promotes negativity about religion, which is bound to impact how people react to Christianity, too.
One problem is that the word religion is almost impossible to define since there is such a variety of religions. For example, not all religions are theistic. And where does irreligion fit in? Is atheism a religion? How about secularism as a way of life? There could be no end to what counts as religion.
The Oxford dictionary defines religion as “the belief in and worship of a superhuman controlling power, especially a personal God or gods.” Does that apply to Christians? Certainly it does. And it justifies the separation of the state from oversight of religion: a secular state has no competence or authority over what is beyond life in this world.
Christians would do better to adopt a positive attitude toward religion, since at least religion as defined includes “belief in and worship of” something or someone beyond us. That is a better place to begin than secularism, atheism, or irreligion. Christian apologetics could focus on making “the case for Christ” rather than having to convince materialists that transcendent reality exists.