This isn't a letter but a company document. Should we say "Our business operation is based on standard industry practices" or "Our business operations are based on..."? Could you give some guidelines on using with/without "s" for this word? Thanks!
You can really use either one you wish. The meanings are the same. 'Operation' is an uncountable noun for the process; 'operations' is the plural countable noun for the various manifestations of 'operation'.
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not right

When we talk about Business - it should be 'Operations' because any business is combination of various activities associated in that particular business and nothing in a business can be done in isolation from its' related activities. Operation literally means process and Business is always a combination of interrelated processes and therefore, business operations.