If I understand correctly, I have to use one of these 3 forms depending on the case:

verb: drop out

noun: dropout

modifer: drop-out

Are the following 7 examples spelled correctly in British English?

1) Predicting student dropout in higher education

2) Student drop-out prediction

3) A student who dropped out

4) We consider these students as dropouts

5) Most drop-out students

6) 50% of the dropouts

7) Create drop-out prediction models

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  • It needs to be noted that "dropout" (in several of the above presentations) is often used in a technical sense, everywhere from electronics to bicycles. – Hot Licks May 1 at 15:56
  • 1
    Cambridge dictionary has drop out as a "phrasal verb", and dropout as a noun. It does not have an entry for drop-out - but you could check other dictionaries. – TrevorD May 1 at 16:25

Dictionaries generally agree that drop out is the verb form and dropout or drop-out is the noun form. (See Merriam-Webster, which has dropout for the noun, and the Oxford English Dictionary, which has drop-out for the noun.) This fits a general pattern for nouns formed from phrasal verbs: as a noun they tend to form a word without a space or a hyphenated word:

go-ahead, breakdown, mix-up

The same ambiguity persists for the adjective. Collins Dictionary lists dropout as an adjective and noun form, noting "also drop-out." So both forms are used for nouns and adjectives.

If you go by frequency, dropout is about ten times more frequent in the Corpus of Contemporary American English than drop-out (around 2600 compared to around 250). The Ngram search is flawed with hyphenation but generates a similar result.

One final factor is that compound adjectives that express a single idea are often hyphenated. So if you wanted to conform to this rule, the adjective form would be drop-out.

So it's your decision how you use the noun and adjective forms. You can technically use dropout for both, use drop-out to distinguish the adjective from the noun, or even go against common usage and use drop-out for both. You make the call.

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