Use as either singular or plural in meaning but always with a singular verb; that is, always write data is (or any other singular verb) whether you mean information (singular) or a collection of facts (plural). If you want to make it clear that you are referring to a plural, use facts or numbers instead.

Do not use datum. Do not write data are.

• The data shows that 95% of users prefer a graphical interface.
• The data gathered so far is incomplete.