There are two terms used for pairs of words (in the same or different languages) that look similar but are actually unrelated: false friend and false cognate. Are these terms synonymous? If not, what's the difference?
They are distinct.
True cognates, true friends
Words with a common etymology and modern form and meaning. These are extremely numerous, of course.
True cognates, false friends
Words with a common etymology but which have shifted to have different meanings.
False cognates, true friends
Words etymologically unrelated that nevertheless now have similar meanings (typically by coincidence, but sometimes by influence/reinforcement).
False cognates, false friends
These are completely unrelated words that happen to look similar: