TASK DEFINITION: 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.
PROBLEM: Sentence1: Urine leaves the body through a sphincter in the process of urination. 
Sentence2: urine leaves the body upon relaxation of a muscle.

SOLUTION: Urine

PROBLEM: Sentence1: a stopwatch is used to measure time. 
Sentence2: Time can be measured with a clock or watch.

SOLUTION: measure

PROBLEM: Sentence1: Coral is the calcite shell of the coral animal. 
Sentence2: calcite shells form large colonies in shallow tropical water.

SOLUTION:
calcite