Spicula is a term commonly used in anatomy, biology and geology. It refers to small pointed structures, such as the pointed projections on the ends of bones or the needle-like crystals found in rocks. There are a number of synonyms that can be used for spicula. In the context of anatomy, terms such as spines, protuberances, or projections can be used. In biology, synonyms include thorns, spikes, or barbs. When referring to geological features, terms such as crystals, shards, or fragments may be used. Regardless of the context, all of these synonyms refer to sharp, pointed structures that are an important feature of many natural forms.