Is "notations" a proper English word?

Some of my colleagues use the word "Notations" as the title of a section of a paper which defines their terms. I think the proper word is "Notation". I could not find notation on any list of words with the same plural as singular (but I did find the phrase "marginal notations," which I believe is correct, although not commonplace). Is "notations" an acceptable plural for "notation"? Same question for "informations".

Solution 1:

When used as a mass noun to indicate a set of symbols relating to a topic, it is used in the singular form.

Examples: Algebraic notation, algorithmic notation, set notation, percussion notation, etc.

When used as a count noun relating to multiple sets of symbols, it is used in the plural form.

Examples: new terminologies and notations

Source: http://www.oxforddictionaries.com/definition/english/notation?q=notations

Similar words: Audience/audiences, population/populations, people/peoples

Solution 2:

For the title of a section in a paper, the usual word is 'Notation'. A reviewer should correct yours to this.

But if for some reason everyone in your particular academic community happens to use 'Notations', then use that.