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: Instead, the body is covered with a protective shell of bony armor. 
Sentence2: Most mollusks have protective of bony armor.
armor

Sentence1: Runoff water is wasted water. 
Sentence2: Streams may start with wasted water.
wasted

Sentence1: Invertebrates are animals that lack a vertebral column, or backbone. 
Sentence2: Fish are aquatic animals that do not lack a vertebral column.

column