witness
目击(亲眼在场看到,可作证;或时期/地点「经历了某事」)
observe
观察(系统性、有意识地注意或研究某事物,不强调「在场可作证」)
Several bystanders witnessed the accident and provided statements to the investigating officers.
几名旁观者目睹了事故经过,并向调查人员提供了陈述。
Researchers spent three years observing the social behaviour of chimpanzees in their natural habitat.
研究人员花了三年时间在自然栖息地观察黑猩猩的社会行为。