There are certain commonly used terms which need a precise definition because of existing confusion. The following definitions are recommended. All terms are defined as they relate to otoliths (Prince and Pulos, 1983; Anon., 1985):
| annual zone | : Structural feature of the otolith corresponding to the growth during a complete year of life. |
| annulus | : The theoretical boundary between two successive annual zones. |
| check | : A boundary between two growth zones, not necessarily annual. |
| focus | : The hypothetical or real origin of the otolith; synonymous with nucleus or core. |
| opaque zone | : A zone that inhibits the passage of light. In transmitted light opaque zones appear dark, in reflected light they appear bright (white). |
| radius | : A defined measure from a focus to a specific point. |
| translucent zone: | A zone that allows the passage of light. In transmitted light translucent zones appear bright, in reflected light they appear dark. |
| validation | : The confirmation of the temporal meaning of a growth increment. Analogous to determining the accuracy of age determination; used in reference to true age. |
| verification | : Determining the precision (reproduceability) of age determination, used in reference to the precision of estimated age. |
