Basal or basilar is a term meaning base, bottom, or minimum.
- Basal (anatomy), an anatomical term of location for features associated with the base of an organism or structure
- Basal (medicine), a minimal level that is necessary for health or life, such as a minimum insulin dose
- Basal (phylogenetics), the "base" or earliest clade to branch in a larger clade
- Basal sliding, the act of a glacier sliding over the bed before it due to meltwater under the ice acting as a lubricant