An ELT Glossary : Notional Syllabuses

A notional syllabus (also called a notional/functional syllabus)  is one whose language content is organised according to meanings which the learner needs to express, (making requests, expressing past events, expressing hypothetical present meaning, describing location) and the exponents which are used to communicate them. For example, for function Making Requests, possible  exponents would be :

Can/Could you + infinitive  (Can  you open the window?)
Would you mind + Ving (Would you mind opening the window)
I wonder if you could/would mind  (I wonder if you'd mind opening the window.)

Notional/functional syllabuses were the basis of the early communicative approach, and are associated with the work of the Council of Europe in the early 70s, led by Wilkins, van Ek, Richterich and Trim.

Further reading

Wilkins, D.A (1972) Grammatical, Situational and Notional Syllabuses, Council of Europe