Q.Explain the term thecodont and diphyodont.

These two terms describe features of mammalian (including human) dentition:

Thecodont: Teeth are set into individual sockets in the jawbone (the term comes from "theca" = socket/case). This arrangement anchors each tooth firmly, in contrast to teeth that are simply fused to the surface of the jaw (acrodont) or attached along the inner side of the jaw (pleurodont), as seen in some other vertebrates.

Diphyodont: An individual develops two successive sets of teeth over a lifetime — the first set, the deciduous or milk teeth, appear in childhood and are later shed and replaced by a permanent (adult) set of teeth. This is in contrast to animals that grow teeth continuously throughout life (polyphyodont). …

Break each term down by its defining feature: thecodont refers to HOW the teeth are anchored (in bony sockets); diphyodont refers to HOW MANY set …

• Confusing diphyodont (two sets of teeth over a lifetime) with heterodont (different types of teeth at one time) — they describe different aspects of dentition. …