The Five Vocal Origins of the Letters

The 22 letters of the Hebrew alphabet divide into 5 phonetic groups, based on their origin in the mouth's vocal system:

• the throat: א (alef) ח (chet) ה (hei) ע (ayin)
• the palate: ג (gimel) י (yud) כ (kaf) ק (kuf)
• the tongue: ז (zayin) ש (shin) ס (samech) ר (raish) צ (tzadik)
• the teeth: ד (dalet) ט (tet) ל (lamed) נ (noon) ת (tav)
• the lips: ב (bet) ו (vav) מ (mem) פ (pai)

Phonetically, any two letters of the same origin can be interchanged. Thus, there are many Hebrew words whose proximity in meaning stems from their phonetic equivalence.

These letter interchangings are often used in Kabbalistic analysis of Hebrew words of phrases, particularly from the Bible and the Talmud.

Source: www.inner.org