س ن نrunning on smoothly; a way

السنة · al-sunna · the way, the practice

• Met in: V1 p11 ¶1d: «الذين يحيون سنتي ويعلمونها عباد الله», "those who bring my sunna to life and teach it to the servants of Allah".
• Dictionary form: سُنَّة. Lane: "A way, course, rule, mode, or manner, of acting or conduct or life or the like"; "it signifies also [particularly] a way of acting &c. that is commended, or approved, and right".
• Pattern: فُعْلَة (fuʿla).
• Meaning here: The Prophet's ﷺ way: «سنتي», "my sunna". Those who bring it back to life and teach it are his successors.

Ibn Faris, Maqāyīs al-Lugha, root سنن, vol 3, p 60

السين والنون أصل واحد مطرد، وهو جريان الشيء وإطراده في سهولة، والأصل قولهم سننت الماء على وجهي أسنه سنا، إذا أرسلته إرسالا

One regular origin: a thing running on, smoothly and steadily. Its root is the saying "I poured water over my face", when you let it run freely. Then: «ومما اشتق منه السنة، وهي السيرة. وسنة رسول الله عليه السلام: سيرته», "among what comes from it is al-sunna, a way of life; and the sunna of the Messenger of Allah is his way of life". It is so called, he says, «لأنها تجري جريا», "because it runs on".

Urdu bridge

سنت (the Prophet's ﷺ way, and a sunna prayer), سنتیں and اہلِ سنت are everyday Urdu. (to be confirmed)

Quran

21 words from this root (Quranic Arabic Corpus). Most common: سُنَّة (a way) ×16, مَّسْنُون ×3.

سُنَّةَ ٱللَّهِ فِى ٱلَّذِينَ خَلَوْا۟ مِن قَبْلُ وَلَن تَجِدَ لِسُنَّةِ ٱللَّهِ تَبْدِيلًا

[This is] the established way of Allah with those who passed on before; and you will not find in the way of Allah any change.

Surah Al-Ahzaab (33), ayah 62 · Saheeh International

Why this ayah: «سُنَّةَ ٱللَّهِ», "the established way of Allah": the same word, here for Allah's own way, which "you will not find … any change" in.

In the Ihya

السنة: 589 times in the Ihya (the spelling of both سُنَّة, a way, and سَنَة, a year).