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. These may be functions (or illocutionary acts) such as making requests, apologising, giving directions, or conceptual categories (notions) such as place, time and emotions,  and the exponents which are used to communicate them. For example, for the function Making Requests, possible functional 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.)

For Describing Location, notional exponents would include such grammatical categories as prepositions of place (on, in, under, in front of etc)

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

Nunan, D. Syllabus Design, OUP