Free modifiers (or “sentence adjuncts”) are grammatical structures that do not sound complete (unlike independent clauses) and that are set off from other structures with a pause (in speech) or a punctuation mark (in writing).
They can be identified by these characteristics:
1. they are not necessary to make the sentence complete (they are inessential);
2. they can be located anywhere in a sentence — beginning, middle, or end (viz. initial, medial and final modifiers);
3. they are most often punctuated with commas; and
4. they are usually identified by the first word in the phrase.
There are six kinds, namely, one each for five parts of speech (noun, verb, adjective, adverb, preposition; the three other parts of speech — pronoun, conjunction and interjection — aren’t normally used in free modification) and one comprising five types of clause:
- nominal cluster: noun, e.g. A cautious soul, Jim opened the door against his best judgment (a.k.a. an appositive);
- verbal cluster: present participial, past participial, infinitive, e.g. Jim opened the door to see what was up (= verbal [“to see”] + modifiers or a noun);
- adjectival cluster, e.g. Curious about the kerfuffle outside, Jim opened the door (= adjective that modifies a noun: here, “Jim”);
- adverbial cluster, e.g. Gingerly, Jim opened the door (= adverb that modifies the verb — or the sentence as a whole);
- prepositional phrase, e.g. With bat in hand, Jim opened the door. (N.B. prepositional phrases are usually adverbial); and
- altered clause: a. subordinate; b. free relative (which, for which); c. free absolute, e.g. His bat at the ready, Jim opened the door (= noun + free modifier); d. free that, e.g. His goal — that the door be open — was achieved; e. quote-attributing clause.
- resumptive modifiers, e.g. He finally faced his biggest fear, the fear that had plagued him since moving in; and
- summative modifiers, e.g. He finally faced his biggest fear, a victory against all odds (N.B. they can modify any kind of word, phrase or clause).
N.B. If it isn’t clear to what modifiers refer, they are said to “dangle,” “disrupt,” be “misplaced” or “squint” (Mark Nichol, “5 Types of Modifying Mistakes,” Daily Writing Tips, 12 Aug. 2012).