Some sample entries:

CLEFT

Any of various constructions in which some element of a sentence is removed from its normal position and certain extra words are added to highlight the cleft. The purpose of a cleft is to place the clefted element into FOCUS. For example, starting with the sentence Mike wants a new car, we can form an IT-CLEFT to focus either on Mike (It's Mike who wants a new car) or on a new car (It's a new car Mike wants). Or we can form a WH-CLEFT (or PSEUDO-CLEFT) to focus on a new car: What Mike wants is a new car or A new car is what Mike wants.

MAIN CLAUSE

A CLAUSE which is capable of making a complete sentence by itself; a clause which is not a SUBORDINATE CLAUSE. A sentence always contains at least one main clause, and a SIMPLE SENTENCE consists only of a single main clause. In the simple sentence Susie finished her drink, the whole sentence is the main clause. In the COMPOUND SENTENCE Susie cooked dinner, and Natalie did the washing-up, there are two main clauses connected by and. See also MATRIX CLAUSE.

TOPICALIZATION

The construction in which a phrase is moved out of its ordinary position to the beginning of the sentence in order to serve as a TOPIC. Consider the following sentence: I can't recommend this book. It is possible to move the noun phrase this book to the front of the sentence in order to produce This book I can't recommend, in which this book is topicalized: that is, the new sentence is a comment about this book.