What is tawhid in Islam?

What the word means

Tawhid comes from the Arabic root w-h-d, "one". It literally means "making one" or "affirming oneness". In practice it means you believe Allah alone created and runs the universe, and you direct your worship, prayers and deepest trust to Him alone. The shortest summary is Surah al-Ikhlas, which the Prophet ﷺ described as equal to a third of the Quran:

The three aspects scholars describe

Many scholars explain tawhid in three parts to make it easier to learn:

• Oneness of Lordship (rububiyyah): Allah alone creates, sustains, gives life and causes death.
• Oneness of worship (uluhiyyah): only Allah is prayed to, bowed to and relied on in worship. Not saints, prophets, idols or angels.
• Oneness of names and attributes (asma wa sifat): Allah is described as He described Himself, the Merciful, the All-Knowing, without comparing Him to His creation.

Other scholars teach the same ideas with different headings. The core is the same: one God, worshipped alone.

Shirk: the opposite of tawhid

Shirk means associating partners with Allah, such as worshipping another being alongside Him or believing someone shares His powers. It is considered the gravest sin in Islam. That's why Muslims don't pray to the Prophet ﷺ either. See Do Muslims worship Muhammad? Still, Allah's door is always open: anyone who turns away from shirk and returns to Him is forgiven.

Why tawhid matters in daily life

The Prophet ﷺ once told Mu'adh that Allah's right over His servants is that they worship Him and associate nothing with Him, and their right over Allah is that He will not punish those who do so (Sahih al-Bukhari 2856). Tawhid is also freeing. You don't need to please a hundred powers, fear luck charms or seek approval from everyone. You turn to One who hears every dua. This is also why Muslims say the God of Abraham is the same God. See Do Muslims and Christians believe in the same God? and Why do Muslims call God Allah?