/ ˌɔːltəˈreɪʃn; NAmE / noun
1.
[ C ] a change to sth that makes it different :
major / minor alterations
They are making some alterations to the house.
an alteration in the baby's heartbeat
2.
[ U ] the act of making a change to sth :
The dress will not need much alteration.
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WORD ORIGIN
late Middle English : from Old French , or from late Latin alteratio(n-) , from the verb alterare , from Latin alter other.