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1. A class of relationship between two organisms where one organism benefits without affecting the other. It compares with mutualism, in which both organisms benefit, amensalism, where one is harmed while the other is unaffected, and parasitism, where one benefits while the other is harmed. (

2. A sharing of the same environment by two organisms where one species benefits and the other is unaffected. An example is barnacles on whales. (

3. An association between two organisms in which one benefits and the other derives neither benefit nor harm. (Google Dictionary)

4. The relation between two different kinds of organisms when one receives benefits from the other without damaging it. (

5. A relation between two kinds of organisms in which one obtains food or other benefits from the other without damaging or benefiting it. (

6. The act of eating together; table fellowship. (

Word origin: From Medieval Latin commensalis, from com- “together” + mensa (genitive mensalis) “table.”

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