The English translation of the Arabic word "شاهد" (pronounced "shahid") depends on the context in which it is used. Here are some of the most common translations:
Witness: This is the most common translation of "شاهد" when it is used to refer to someone who has seen or observed something, such as a crime or an accident. For example, you could say "المشاهد رأى القاتل يطعن الضحية" (al-shahid ra'a al-qatil yaṭ'in al-ḍaḥīyah), which means "The witness saw the murderer stab the victim."
Eyewitness: This is a more specific term for a witness who has seen a crime or other event firsthand. For example, you could say "الشرطة تبحث عن شهود عيان للحادث" (al-shurta tabḥa 'an shuhūd 'aīyān lil-ḥādith), which means "The police are looking for eyewitnesses to the accident."
Spectator: This is a more general term for someone who watches something, such as a sporting event or a performance. For example, you could say "كان هناك الآلاف من المشاهدين في الحفل" (kāna ḥanāk al-āfā min al-mashāhidīn fī al-ḥafl), which means "There were thousands of spectators at the concert."
Observer: This is a more formal term for someone who studies or examines something, often for scientific purposes. For example, you could say "أجرى العلماء تجارب على مجموعة من المراقبين" (ajrā al-ʿulamā' tajārib ʿalā majmūʿah min al-murāqibīn), which means "The scientists conducted experiments on a group of observers."
In addition to these specific translations, "شاهد" can also be used in a more general sense to mean "see" or "watch." For example, you could say "شاهدت التلفزيون" (shahadt al-tilfazīyūn), which means "I watched TV," or "شاهدت الشمس تغرب" (shahadt al-shams taġrub), which means "I watched the sunset."
I hope this helps! Let me know if you have any other questions.