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


question:
Sentence1: Mollusks are invertebrates such as the common snail. 
Sentence2: snails have no backbone.
answer:
snail


question:
Sentence1: the gravitational pull of the Moon on Earth 's oceans causes the tides. 
Sentence2: Tides are the rising and falling of ocean's water.
answer:

tides