In general, words should be used for numbers from zero through nine, and numerals should be used from 10 onwards. This is true for both cardinal numbers (e.g., two, 11) and ordinal numbers (e.g., second, 11th).
When should you write numbers as words?
Numbers up to nine should always be written in words, anything higher than nine can be written in numerals. Alternatively, some guides suggest that if you can write the number in two words or fewer then use words rather than numerals.
What is it called when you use numbers for words?
Most commonly, a numeronym is a word where a number is used to form an abbreviation (albeit not an acronym or an initialism). ... These word shortenings are sometimes called alphanumeric acronyms, alphanumeric abbreviations, or numerical contractions.
