بعين

In a sentence

• رأيت الحادث بعيني.

  I saw the accident with my own eyes.

  Here, بعيني refers to seeing directly with one's own eyes as a means of emphasizing personal witness.

• أتابع الموضوع بعين المراقب.

  I follow the matter with the eye of an observer.

  Here, بعين metaphorically conveys the perspective or viewpoint of an observer.

• نظر إلى المشكلة بعين التفاؤل.

  He looked at the problem with an eye of optimism.

  Here, بعين represents a metaphorical viewpoint or attitude towards the problem, namely, optimistic.