Does کَوکَب mean star or planet in the holy Quran?

In this Iranian website it is stated that the word کَوکَب means star in the holy Quran: > (فَلَمَّا جَنَّ عَلَیْهِ‌ اللَّیْلُ رَای‌ کَوْکَباً) «چون شب او را فرا گرفت ستاره‌ای دید.» Surat al-An'am, verse 6. Translation of the Persian translation (pardon me please if a little incorrect): When the night cast on him, he saw a star. But doesn't star translate to نَجم and اَختَر in Arabic? We have also verses that contain نَجم with the meaning of star: > (وَ النَّجْمِ‌ اِذا هَوی‌) قسم به ستاره آن زمان که فرود می آید (Swear to star, when it comes down) Surat al-Najm, verse 1. I also searched for مِرّیخ in Arabic Wikipedia : > المِرِّيخ أو الكوكب الأحمر هو الكوكب الرابع من حيث البعد عن الشمس في النظام الشمسي... Ttanslation: Mars or the red planet is the fourth planet in the aspect of distance from the Sun in the solar system... کَوکَب clearly means planet here. I am confused. Does کَوکَب mean star or planet in the holy Quran? Maybe it meant star at the time of Prophet Muhammad (P.B.U.H)? But there is also a Quran verse (in the surah al-Yusuf) that کَوکَب sounds planet to me in! > اِذ قالَ یوسُفُ لِأبیهِ یا اَبَتی إنّی رَأیتُ اَحَدَ عَشَرَ کَوکَبا وَالشَّمسَ وَالقَمَرَ رَأیتُهُم لی ساجِدین Translation: When Joseph told his father: "oh father, I saw (in my dream) that eleven planets(?) and the Sun and the Moon were bowing down to me". I can't think کَوکَب means star here! Because the Sun is a star itself and also, it's always the planets that come after the Sun. The verse also calls the Moon.