Vietnamese

Six in the standard Hanoi dialect (level, falling, rising, dipping-rising, high broken, low broken), five in the southern Saigon variety (which merges two of the northern tones). Tones are part of every word — bà (grandmother), bá (eldest aunt), bả (poison), bã (residue), and bạ (random) all share the same consonants and vowel but differ entirely in meaning.

Quốc ngữ (national script) was developed by Portuguese, Italian, and French Catholic missionaries in the 17th century, most famously by the Jesuit Alexandre de Rhodes. It replaced earlier scripts based on Chinese characters (chữ Nôm) and gradually became the standard. By the early 20th century, French colonial administration had pushed it into universal use, and it's been the sole official script since.

No. Verbs don't conjugate for person, number, or tense. Nouns don't change for plural or case. Time is shown by adverbs and aspect particles (đã for completed past, đang for ongoing, sẽ for future). The grammatical workload sits in word order, particles, and the tone system.

Not by family — Vietnamese is Austroasiatic, Chinese is Sino-Tibetan. But the two have been in contact for over two thousand years, and Vietnamese borrowed roughly 30–60% of its vocabulary from Chinese (Sino-Vietnamese), especially in formal, technical, and academic registers. The result is grammatical separation but heavy lexical overlap.

The grammar is unusually light — no inflection means no conjugation tables. The Latin alphabet shortens the script-learning phase. The hard parts are the tone system, which most non-tonal-language speakers find takes months to internalize, and the rich pronoun system that varies by relative age, gender, and relationship to the listener.