To notice or view, especially carefully or with attention to detail.
To take note of and celebrate (a holiday or similar occurrence); to follow (a type of time or calendar reckoning).
To comment on something; to make an observation.
To follow or obey the custom, practice, or rules (especially of a religion).
To notice, observe, learn, or understand, especially something otherwise overlooked.
To adopt a practice in which others already engage.
To continue or build upon (for example, a task, analysis, or narrative), beginning from a point at which someone has previously stopped.