Generate an overlapping word between the given two sentences. When you find the overlapping words, they don't have to match exactly, e.g., "survival" and "survive" are valid overlapping words. Little words like "the" or "of" don't count! You must generate significant words which are not the stop words.

Sentence1: an image in a mirror is formed by reflecting light. 
Sentence2: mirrors can be seen with our eyes.
mirror

Sentence1: the uterus is used in reproduction. 
Sentence2: Reproduction uses the same organ as menstruation.
reproduction

Sentence1: Rock debris is also know as sediment. 
Sentence2: Breaking apart rocks can cause sediment.

sediment