ACT English: Master Irregular Plural Nouns and Agreement

Irregular plural: datum→data, criterion→criteria, analysis→analyses, phenomenon→phenomena, alumnus→alumni, cactus→cacti (or cactuses). Example: "The data shows trends" is correct; "The datas show" is wrong because "data" is plural already. Another example: "Each criterion is important" (singular) versus "All criteria are important" (plural). On ACT English, irregular plurals trip up students who aren't familiar with Latin or Greek roots, but memorizing 10-15 common irregulars covers most test questions.

Rule: When unsure, check whether the word ends in -a (usually plural, like data, criteria, phenomena) or -on (usually singular, like phenomenon, criterion). If it ends in -a, treat it as plural.

Mistake 1: Using singular verb with plural "data." "The data is..." should be "The data are..." (even though it sounds awkward). Mistake 2: Treating singular "criterion" as plural. "The criterion are X" should be "The criterion is X." Mistake 3: Mixing forms incorrectly. "These criteria suggests..." should be "These criteria suggest..." Irregular plurals break normal verb agreement rules; memorize the tricky ones.

Checklist for ACT: Scan every plural noun. Ask: Is this a known irregular? If yes, verify the verb agrees with the correct number. This 10-second check prevents careless errors.

Sentence 1: "The analysis (is/are) comprehensive." Correct: "is" (analysis is singular; analyses is plural). Sentence 2: "All criteria (has/have) been met." Correct: "have" (criteria is plural). Sentence 3: "This phenomenon (occurs/occur) rarely." Correct: "occurs" (phenomenon is singular; phenomena is plural). Sentence 4: "The data (suggests/suggest) a trend." Correct: "suggest" (data is plural in modern usage, though older usage treated it as singular). Complete all four, then rewrite each with the opposite number (singular to plural or vice versa) to lock in understanding.

Challenge: Write two sentences using "alumni" and two using "alumnus." Verify agreement in each.

ACT English values precision. Writers who ignore irregular plurals appear careless, and college professors notice. Expect 1-2 irregular plural or agreement questions per English section, often disguised as subject-verb agreement errors.

This week, create a flashcard list of 15 irregular plurals. Review them daily. By test day, you'll recognize irregular forms instantly and avoid agreement mistakes that others miss.