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.
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Question: Sentence1: Homogeneous mixtures are called solutions. 
Sentence2: A homogenous mixture is formed when one substance dissolves in another.

Answer: Homogeneous


Question: Sentence1: Echinoderms lack respiratory and excretory systems. 
Sentence2: echinoids lack a respiratory system.

Answer: respiratory


Question: Sentence1: Amphibians have a relatively complex circulatory system with a three-chambered heart. 
Sentence2: Blood is pumped around the body by a heart .

Answer:
heart