The expressions even as, even so, even if and even though have very different meanings.
Even as means at the same time as. This expression is used to suggest that something is happening exactly when somebody is doing or saying something else.
- Even as the old man lay dying, his children and grandchildren argued over his property.
- Even as the ministers were negotiating a ceasefire agreement, troops kept themselves busy killing innocent civilians across the border.
Here the two activities occur at the same time.
Even if is used to suggest that one situation will remain the same although something else may change.
- Even if I become a billionaire, I will always remain a socialist. (My financial situation may change, but I my ideologies won’t.)
- Even if she invites me, I will not go.
- I will go even if he forbids me.
- I will not permit this even if they kill me.
As you can see, even if refers to the future. Here we are talking about situations that may happen in the future.
Even though is similar to though and although. It just happens to be more emphatic.
- Even though I had a headache, I enjoyed the film. (= Though / although I had a headache, I enjoyed the film.)
- Even though I didn’t understand a word, I kept smiling.
- Even though can refer to the past. It can also refer to the present.
- Even though she works hard, she does not earn enough money to support her family.
Even so means ‘however’. It is used to introduce a statement that might surprise the reader.
- She is quite beautiful. Even so, I don’t like her.
- She comes across as an arrogant woman. Even so, you can’t help liking her.
Crashes are rare, but, even so, passengers should wear seat belts.