Gerund use meaning 'the act of observing'; typically uncountable.
Definitions
The act or process of watching something carefully in order to gain information. Accurate observing of the birds’ behavior takes patience.
observinggerund / present participle More precise tagging for present-participle adjective.
Translations
She is very observing and notices every detail.
Она очень наблюдательная и замечает каждую деталь.
Definitions
Attentive or watchful, especially in noticing details. The observing student quickly noticed the changes in the experiment's results.