Thansk! The background is a long story

and I will post it a few days later seeking advices for dealing with some other conflicts with this company.

This particular term is actually their one party's modification to the existing contract, which was emailed to me 3 months ago and I just ingnored it as I had believed it should be unenforceable unless it is mutually aggreed under the given circumstances. If I had known "bimonthly" could mean half month instead of 2 months, I would have terminated the business with them. When I realized the second different meaning, it was already passed their stipulated new rate starting date.However, they are still charging me at the same rate originally agreed, not at the altered one. So there would be no law suit. ( A little disappointed, isnt't it? :-))I was just curious about how it is legally interpreted when a word is ambiguous and it is also the key word in a contract. Thank you again for sharing your knowledge.