Word 'mange '
Mange means eat/am eating. Now when this word is used in some French sentence, how to know, how to know which tense is being referred to, here?
I forgot about "I do eat" - well pointed out. This would be a rather emphatic response to someone who, perhaps, accuses you of not eating (maybe being anorexic). For example:
"Tu ne mange jamais rien !" → "You never eat anything!"
to which the response might, indignantly (or defensively) be:
"Si, je mange !" → "Yes, I do eat!"
Manger means "to eat". When conjugated in the present, it is this:
As you can see, "mange" is used in the present tense with "je" and "il/elle/on". However, this changes with different tenses. I would suggest going to wordreference.com and looking at all of the conjugation forms of "manger" in each tense. ^ ^