These are morphemes that can function independently as full words. Using Morphology to Teach Vocabulary - Keys to Literacy

Morphemes are the smallest units of meaning in a language. Unlike syllables, which are units of sound, a morpheme must carry its own distinct semantic or grammatical information and cannot be divided further without losing that meaning. For example, the word "dogs" contains two morphemes: "dog" (referring to the animal) and "-s" (indicating plurality). Types of Morphemes

Linguists generally classify morphemes into two primary categories based on whether they can stand alone or must be attached to other units. 1. Free Morphemes