Slot fillers are words or phrases that are used to fill in the gaps in a sentence. They are often used to make a sentence sound more natural and to provide additional information. Examples of slot fillers include conjunctions, pronouns, and adverbs. The term 'slot fillers' comes from the idea that these words fill in the 'slots' in a sentence. TABS (4 letters) is an acronym for 'Transitional Adverbs, Pronouns, and Subordinating Conjunctions'. These are all types of slot fillers that can be used to fill in the gaps in a sentence.