The collection of all collections that are "object-like" in at least one respect. A collection <code><b>COL</b></code> is object-like just in case there is some sense of 'part' according to which any (or nearly any) given proper part of an instance of <code><b>COL</b></code> is <i>not</i> itself an instance of <code><b>COL</b></code>; when this happens <code><b>COL</b></code> is said to be object-like with respect to that sense of 'part'.
<p/>
More precisely, for a collection <code><b>COL</b></code> to be an instance of ObjectType it is sufficient that there be some specialization <code><b>PARTPRED</b></code> of properParts such that, for any <code><b>OBJ1</b></code> and <code><b>OBJ2</b></code>, if <code>(isa <b>OBJ1</b> <b>COL</b>)</code> and <code>(<b>PARTPRED</b> <b>OBJ1</b> <b>OBJ2</b>)</code> both hold, then <code>(isa <b>OBJ2</b> <b>COL</b>)</code> does <i>not</i> hold. (Also sufficient for <code><b>COL</b></code>'s being an object-type is that there be some specialization <code><b>INVPARTPRED</b></code> of the <i>inverse</i> of properParts (see genlInverse) such that <code>(<b>INVPARTPRED</b> <b>OBJ2</b> <b>OBJ1</b>)</code>, with everything else remaining the same as above.) Note that neither of the above sufficient conditions for <code><b>COL</b></code>'s being an object-type is strictly necessary: some exceptions are allowed. Thus as long as either one of the above conditionals holds in <i>nearly</i> all cases, <code><b>COL</b></code> should be considered an instance of ObjectType.
<p/>
Here are two examples. Consider Automobile. Take an instance of that, say my car. Now consider one of the proper physicalParts of my car, say the steering wheel. The steering wheel is <i>not</i> an instance of Automobile. And the same would be true for any proper physical part of any car. So Automobile is an ObjectType. Consider CalendarYear. No proper timeSlices of a year is itself a year. So CalendarYear is an ObjectType.
<p/>
See StuffType for the contrasting (though not disjoint) notion of being stuff-like.