و-ح-د
5 words from this root family
Sunday
In the Arab world, Sunday is traditionally the first day of the week
alone / only / sole
Feminine form: waḥīda (وَحيدة). From the same root as wāḥid (واحِد, one) and waḥda (وَحدة, unity).
monotheism / oneness of God
Form II maṣdar from وَحَّدَ (to make one/declare one). Related: أَحَدٌ (one), وَاحِدٌ (one/unique). The central theological concept of Islam.
Surah al-Ikhlāṣ (112) is called the essence of tawḥīd. The Prophet ﷺ said it equals one-third of the Quran in meaning.
divine unity / absolute oneness
Abstract noun (فَعْلَانِيَّة pattern). From وَاحِدٌ (one). The theological term for God's absolute oneness. Related to تَوْحِيدٌ (q220) but more abstract and philosophical.
Waḥdāniyyah is the most fundamental concept in Islamic theology — God is not merely 'one among many' but uniquely, absolutely One in essence, attributes, and actions.