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: Diurnal cycles Diurnal cycles are the daily cycles of light and darkness. 
Sentence2: Plants detect and respond to diurnal cycles.
Diurnal

Sentence1: Most bryophytes are small. 
Sentence2: Most in the same group as mosses are small.
small

Sentence1: harming an animal species causes that animal 's population to decrease. 
Sentence2: If mortality is greater, then the population decreases.

decrease