Aristotle Categories 1a20-1b9:

• Of things there are: (a) some are said of a subject but are not in any subject. For example, human is said of a subject, the individual, human, but is not in any subject. (b) Some are in a subject but are not said of any subject. (By 'in a subject,' I mean what is in something, not as a part, and cannot exist separately from what it is in.) For example, the individual knowledge-of-grammar is in a subject, the soul, but is not said of any subject; and the individual white is in a subject, the body (for all color is in a body), but is not said of any subject. (c) Some are both said of a subject and in a subject. For example, knowledge is in a subject, the soul, and is also said of a subject, knowledge-of-grammar. (d) Some are neither in a subject nor said of a subject, for example, the individual man or the individual horse- for nothing of this sort is either in a subject or said of a subject. Things that are individual and numerically one are, without exception, not said of any subject, but there is nothing to prevent some of them from being in a subject--the individual knowledge-of-grammar is one of the things in a subject.