§ 469. Connectives are linking-words considered as a secondary part of the sentence. They are mostly prepositions and conjunctions.
She played and sang to him. (London).
Connectives differ from the previously mentioned secondary parts of a simple sentence in not being, as a rule, adjuncts of certain head-words.
a) They usually connect two words both or neither of which
might be regarded as their head-words;
b) The words they connect belong to various parts of speech.
With conjunctions this refers to both right-hand and left-
hand connections (see § 358). With prepositions it refers
279.
1 The Structure of American English. New York, 1958, pp. 278— Ib