observe

To be or become aware of, especially through careful and directed attention; notice.

To watch attentively.

To make a systematic or scientific observation of.

To say casually; remark.

To adhere to or abide by; comply with.

To act in acknowledgment of (a holiday, for example); keep or celebrate.

To maintain (silence or a period of silence), as out of respect for someone who has died.

To take notice.