A linguistic unit can enter into relations of two different kinds.

PR are relations based on the principles of similarity. They exist between the units that can substitute one another. For instance, in the word-group A PINT OF MILK the word PINT is in paradigmatic relations with the words bottle, cup, etc. The article A can enter into PR with the units the, this, one, same, etc. According to different principles of similarity PR can be of three types:

are based on the similarity of meaning: a book to read = a book for reading

are based on the similarity of forms. Such relations exist between the members of a paradigm: man – men; play – played – will play – is playing.

are based on the similarity of function. They are established between the elements that can occur in the same position. For instance, noun determiners: a, the, this, his, Ann’s, some, each, etc.

A linguistic unit enters into syntagmatic relations with other units of the same level it occurs with. SR exist at every language level. E.g. in the word-group A PINT OF MILK the word PINT contrasts SR with A, OF, MILK; within the word PINT – P, I, N and T are in syntagmatic relations. SR are linear relations, that is why they are manifested in speech. They can be of three different types:

exist between the homogeneous linguistic units that are equal in rank, that is, they are the relations of independence: you and me; They were tired but happy.

are the relations of dependence when one linguistic unit depends on the other: teach + er – morphological level; a smart student – word-group level; predicative and subordinate clauses – sentence level.

SR are the relations of interdependence: primary and secondary predication.
I saw her dancing
I saw - primary predication
her dancing - secondary predication