“I swear” = I promise / I insist on the truth

Used to emphasize sincerity, honesty, or a strong promise. Example: “I swear I didn’t take your book.” (= I promise / I’m telling the truth)

“to swear” = to use offensive or bad language

Means using rude or insulting words. Example: “He got angry and started swearing at the driver.” (= using curse words / profanity )