Num lock. The Num Lock key exists because earlier 84-key IBM PC keyboards did not have cursor control or arrows separate from the numeric keypad. Most earlier computer keyboards had separate number keys and cursor control keys; however, to reduce cost, IBM chose to combine the two in their early PC keyboards.
The most common rule. The most common and frequently used rule for writing numbers in APA style is determined by whether the number is under 10. All those numbers should be written out in word form, such as four or seven. A number 10 and above is written as a numeral, such as 10, 17, 233.
Grammatical number. In linguistics, grammatical number is a grammatical category of nouns, pronouns, and adjective and verb agreement that expresses count distinctions (such as one, two, or three or more). In many languages, including English, the number categories are singular and plural. Some languages also have a dual, trial, quadral and paucal number or other arrangements. The count distinctions typically, but not always, correspond to the actual count of the referents of the marked noun or pronoun.