The Hamza and Its Types — Hamzat Al-Qat'a and Hamzat Al-Wasl

Definition:
Hamzat Al-Qat'a (Cutting Hamza): A Hamza always pronounced — whether starting speech or continuing. Written with Hamza sign on Alif, Waw, or Ya: "Akala", "Ibrahim", "Ula'ika".
Hamzat Al-Wasl (Connecting Hamza): A Hamza pronounced only at the start of speech; it drops when connected to what precedes it. Written in Mushaf as a bare Alif or with a small Sad: "Intalaga" — read "ntalaga" when preceded by another word.

Rule — Hamzat Al-Wasl occurs in:
• Definite article "Al": "Al-Kitab", "Al-Quran"
• Five- and six-letter past-tense verbs: "Intalaga", "Istaghfara"
• Their verbal nouns: "Intilaq", "Istighfar"
• Imperative of 3-letter verbs with sukoon on first root letter: "Idhhab", "Uktub"
• Specific nouns: Ibn, Ibna, Imru, Imra'a, Ithnan, Ithnataan, Ism

Quranic Example:
"Say: Call upon Allah or call upon Ar-Rahman" [Al-Isra: 110] — Hamza of "ud'u" is Wasl, drops when connected.
"Indeed We have given you Al-Kawthar" [Al-Kawthar: 1] — Hamza of "a'tayna" is Qat'a, always pronounced.

Note:
Vowel of Hamzat Al-Wasl when starting: generally Kasra, except in "Al" (Fatha) and certain imperatives where the first root letter carries a Dhamma.