Verbs end with "-as" when they are in present tense. English uses "I am", "you are", "he is". But in Esperanto, there is just one word for "am", "are", "is" - "estas". Similarly, "kuras" can mean "run" or "runs". Infinitives end with "-i". For example, "esti" means "to be", "povi" means "to can". It is easy to make past tense - always add "-is" ending. To make future tense, add "-os". For example: