Are the words yesterday, today, and tomorrow adverbs or nouns? Oxford Living Dictionaries identifies all three words as an adverb first and a noun second. Etymonline lists yesterday as a noun and adverb but today and tomorrow as only adverbs. Wiktionary defines today and tomorrow as adverbs first and nouns second but yesterday as a noun first and an adverb second. Dictionary.com categories yesterday and today as an adverb, noun, and adjective but tomorrow as only a noun and adverb. How can multiple dictionaries analyze the same three words differently, and what is the best word class for words like yesterday, today, and tomorrow?
The line between grammatical forms is blurry at best, especially among lexical categories like nouns and adverbs. Closed functional classes like pronouns, prepositions, determiners, and conjunctions that do not readily accept new members are much clearer. But open lexical classes that acquire new members readily and constantly are less distinguished.
Grammatical function and grammatical form distinguish one word class from other. The ten grammatical functions performed by nouns and noun phrases are subject, subject complement, direct object, object complement, indirect object, prepositional complement, noun phrase modifier, determinative, appositive, and adjunct adverbial. The seven grammatical functions performed by adverbs and adverb phrases are adjective phrase modifier, adverb phrase modifier, verb phrase modifier, prepositional phrase modifier, adjunct adverbial, disjunct adverbial, and conjunct adverbial. Nouns and adverbs overlap in one function: adjunct adverbial.
Adjunct adverbials are words, phrases, and clauses that modify an entire clause by providing additional information about time, place, manner, condition, purpose, reason, result, and concession. Adjunct adverbials are not constituents of the predicate or the subject but are instead constituents of the entire sentence. An adjunct adverbial can be omitted without changing the grammaticality of the remaining sentence. Both adverbs and nouns can function as adjunct adverbials. For example:
- Nervously he opened the door.
- She blew out her birthday candles happily.
- He recounted the tragic story tearfully to his brother.
- I walked home.
- School ends Friday.
- My husband travels a great deal.
The words yesterday, today, and tomorrow can all function as adjunct adverbials. For example:
- Yesterday I went to the store.
- I read the book yesterday.
- Today the dog dug under the fence.
- A mouse got loose in the house today.
- Tomorrow she is heading to Europe.
- He will take out the trash tomorrow.
To determine the word class of yesterday, today, and tomorrow thus requires further analysis.
The internal structures that distinguish nouns from other grammatical forms are number and possession. Prototypical nouns express grammatical number, which is a grammatical category that expresses count distinctions. English nouns are singular or plural. Singular means one. Plural means not one. The majority of English nouns are regular, taking an –s or –es suffix to form the plural. Prototypical nouns also express possession, which indicates a possession of or some other relationship to another word or phrase. In English, the affixation of the possessive clitic (‘s [apostrophe s] or s‘ [s apostrophe]) forms possessive nouns.
The grammatical forms that distinguish adverbs from other word classes are degrees of modification. Prototypical adverbs express three degrees of modification: positive, comparative, or superlative. The positive form is the base form of the adverb. The comparative form expresses a comparison between two entities in quality, quantity, or degree. The superlative form expresses the highest degree of comparison. The majority of adverbs show no inflectional variation, instead expressing three degrees of modification through periphrasis, or the use of separate words to express a grammatical relationship that is otherwise expressed by inflection. Most adverbs use a syntactic system, taking more to form the comparative and most to form the superlative.
Applying syntactic tests to yesterday, today, and tomorrow reveals that all three words are nouns. All three have plural and possessive forms. For example:
- She has many yesterdays behind her but not many tomorrows ahead. (plural)
- We are all accumulations of our yesterdays, todays, and tomorrows. (plural)
- Your todays are a direct result of the sum of all your yesterdays. (plural)
- All the flowers of all the tomorrows are in the seeds of today. (plural)
- Can you review yesterday’s schedule? (possessive)
- What is on today’s and tomorrow’s agendas? (possessive)
None of the three words have comparative or superlative forms: *more yesterday, *most yesterday, *yesterdayer, *yesterdayest, *more today, *most today, *todayer, *todayest, *more tomorrow, *most tomorrow, *tomorrower, and *tomorrowest.
In addition to passing the syntactic test for nouns, yesterday, today, and tomorrow can also perform other nominal functions. For example:
- Today was the best day of my life. (subject)
- My birthday was yesterday. (subject complement)
- I enjoyed yesterday. (direct object)
- She will give tomorrow some thought. (indirect object)
- He declared the best day ever today. (object complement)
- We bought the cake for tomorrow. (prepositional complement)
- My dad went to Europe yesterday morning. (noun phrase modifier)
- Today’s agenda includes cleaning the bathroom. (determinative)
- Christmas Day, tomorrow, is my favorite day of the year. (appositive)
Conversely, yesterday, today, and tomorrow cannot perform adverbial functions such as adjective phrase modifier, adverb phrase modifier, verb phrase modifier, prepositional phrase modifier, disjunct adverbial, or conjunct adverbial.
Despite the confusion created by the various categorizations in multiple dictionaries, the words yesterday, today, and tomorrow are nouns. All three words have plural and possessive forms, and all three words can perform all ten nominal functions including adjunction adverbial.
Brinton, Laurel J. & Donna M. Brinton. 2010. The linguistic structure of Modern English, 2nd edn. Amsterdam: John Benjamins Publishing Company.
Hopper, Paul J. 1999. A short course in grammar. New York: W. W. Norton & Company.
Huddleston, Rodney. 1984. Introduction to the grammar of English. Cambridge: Cambridge University Press.