Exactly we have 6 tones: thanh ngang (example: ba: three), thanh sắc (bá: to hug), thanh huyền (bà: grandmother), thanh hỏi (bả: bane), thanh ngã (bã: residue), thanh nặng (bạ: haphazardly). When we use different tones we have different meaning. There are 29 letters in the Vietnamese alphabet system which consists of 12 vowels and 17 consonants - There have 12 vowels: a, ă, â, e, ê, i, o, ô, ơ, u, ư, y - From 12 vowels, we have diphthong: ai, ay, ao, au, ây, âu, eo, êu, oi, oa, ôi, ơi, ui, uy, uô, ua, uâ, uơ, ưi, ưu, ưa, ươ, iu, ia, iê, yê - From 12 vowels, we have tripthong: oai, oay, oeo, uôi, uyê, ươi, ươu, iêu, yêu. - There have 17 consonants: b, c, d, đ, g, h, k, l, m, n, p, q, r, s, t, v, x - From 17 consanants, we have 11 consonants clusters: ch, gh, gi, kh, nh, ng, ngh, ph, th, tr, qu - From 17 consanants, we have 8 final consonents: c, ch, m, n, nh, ng, p, t - The dipthongs can be combine with a final consonants: + uy (uy_ch: uych, uy_nh: uynh, uy_t: uyt) + uô (uô_c: uôc, uô_m: uôm, uô_n: uôn, uô_ng: uông, uô_t: uôt) + uâ (uâ_n: uân, uâ_ng: uâng, uâ_t: uât) + uyê (uyê_n: uyên, uyê_t: uyêt) + oa (oa_c: oac, oa_ch: oach, oa_n: oan, oa_nh: oanh, oa_ng: oang, oa_t: oat) + ươ (ươ_c: ươc, ươ_m: ươm, ươ_n: ươn, ươ_ng: ương, ươ_p: ươp, ươ_t: ươt) + iê (iê_c: iêc, iê_m: iêm, iê_n: iên, iê_ng: iêng, iê_p: iêp, iê_t: iêt) + yê (yê_n: yên, yê_t: yêt) A word can combine from: - 1 vowels: o (in central of Vietnam o = cô = aunt) - 1 vowel + 1 final consonant: an toàn = safe (an: a is vowel, n is final consonant) - 1 consonant cluster + 1 vowel: cà chua = tomato (cà: c is consonant cluster, a is vowel, thanh huyền `) - 1 consonant cluster + 1 vowel + 1 final consonant: bán = sell (bán: b is consonant cluster, a is vowel, n is final consonant, thanh sắc ‘ ) Hope it helps

You can combine the vowels and final consonants: - a: ac, ach, am, an, anh, ang, ap at - ă: ăc, ăm, ăn, ăng, ăp, ăt - â: âc, âm, ân, âng, âp, ât - e: éc, em, en, eng, ep, et - ê: êch, êm, ên, ênh, êp, êt - i: ich, im, in, inh, ip, it, - o: oc, om, on, ong, op, ot - ô: ôc, om, on, ông, ôp, ôt - ơ: ơm, ơn, ơp, ơt - u: uc, um, un, ung, up, ut - ư: ưc, ưm, ưng, ưt