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: Capillaries are microscopic vessels. 
Sentence2: Lymph is a fluid that leaks out of microscopic vessels into spaces between cells.
microscopic

Sentence1: a thermometer is used to measure temperature. 
Sentence2: a thermometer is used to measure heat.
a

Sentence1: Carbon dioxide is a greenhouse gas. 
Sentence2: greenhouse gas concentrations in the air have increased over the last decade dramatically.

gas