Pinyin differs from other romanizations in several aspects, such as the following:
Syllables starting with u are written as w in place of u (e.g. ueng is written as weng). Standalone u is written as wu.
Syllables starting with i are written as y in place of i (e.g. iou is written as you). Standalone i is written as yi.
Syllables starting with ü are written as yu in place of ü (e.g. üe is written as yue).
ü is written as u when there is no ambiguity (such as ju, qu, and xu), but written as ü when there are corresponding u syllables (such as lü and nü). In such situations where there are corresponding u syllables, it is often replaced with v on a computer, making it easier to type on a standard keyboard.
When preceded by a consonant, iou, uei, and uen are simplified as iu, ui, and un (which do not represent the actual pronunciation).
As in zhuyin, what are actually pronounced as buo, puo, muo, and fuo are given a separate representation: bo, po, mo, and fo.
The apostrophe (') is used before a, o, and e to separate syllables in a word where ambiguity could arise, e.g., pi'ao (simplified Chinese: 皮袄; traditional Chinese: 皮襖) vs. piao (票), and Xi'an (西安) vs. xian (先).
Eh alone is written as ê; elsewhere as e. Schwa is always written as e.
zh, ch, and sh can be abbreviated as ẑ, ĉ, and ŝ (z, c, s with a circumflex). However, the shorthands are rarely used due to difficulty of entering them on computers.
ng has the uncommon shorthand of ŋ.
Most of the above are used to avoid ambiguity when writing words of more than one syllable in pinyin. For example uenian is written as wenyan because it is not clear which syllables make up uenian; uen-ian, uen-i-an and u-en-i-an are all possible combinations whereas wenyan is unambiguous because we, nya, etc. do not exist in pinyin. A summary of possible pinyin syllables (not including tones), can be reviewed at: pinyin table
[edit] Capitalization and word formation
Although Chinese characters represent single syllables, Mandarin Chinese is a polysyllabic language. Spacing in Hanyu Pinyin is based on whole words, not single syllables. However, there are often ambiguities in partitioning a word. Orthographic rules were put into effect in 1988 by the National Educational Commission (国家教育委员会) and the National Language Commission (国家语言文字工作委员会).
General
Single meaning: Words with a single meaning, which are usually set up of two characters (sometimes one, seldom three), are written together and not capitalized: rén; péngyou, qiǎokèlì (person; friend; chocolate)
Combined meaning (2 characters): Same goes for words combined of two words to one meaning: hǎifēng; wèndá, quánguó (sea breeze; Q&A; 'pan-national')
Combined meaning (4 or more characters): Words with four or more characters having one meaning are split up with their original meaning if possible: wúfèng gāngguǎn; huánjìng bǎohù guīhuà (seamless steel-tube; environmental protection planning)
Duplicated words
AA: Duplicated characters (AA) are written together: rénrén (everybody), kànkàn (to have a look), niánnián (every year)
ABAB: two characters duplicated (ABAB) are written separated: yánjiū yánjiū (to study, to research), xuěbái xuěbái (snow-white)
AABB: A hyphen is used with the schema AABB: láilái-wǎngwǎng (go back and forth), qiānqiān-wànwàn (numerous)
Nouns and names (míngcí): Nouns are written in one: zhuōzi (table), mùtou (wood)
Even if accompanied by a prefix and suffix: fùbùzhǎng (vice minister), chéngwùyuán (conductor), háizimen (children)
Words of position are separated: mén wài (outdoor), hé li (in the river), huǒchē shàngmian (on the train), Huáng Hé yǐnán (south of the Yellow River)
Exceptions are words traditionally connected: tiānshang (in the sky), dìxia (on the ground), kōngzhōng (in the air), hǎiwài (overseas)
Surnames are separated from the given name: Lǐ Huá, Zhāng Sān. If the given name consists of two syllables, it should be written as one: Wáng Jiàngguó.
Titles following the name are separated and are not capitalized: Wáng bùzhǎng (minister Wang), Lǐ xiānsheng (Mr. Li), Tián zhǔrèn (director Tian), Zhào tóngzhì (comrade Zhao).
The forms of addressing people with Lǎo, Xiǎo, Dà and A are capitalized: Xiǎo Liú ([young] Ms. Liu), Dà Lǐ ([great] Mr. Li), A Sān (Ah San), Lǎo Qián ([senior] Mr. Qian), Lǎo Wú ([senior] Ms. Wu)
Exceptions are: Kǒngzǐ (Master Confucius), Bāogōng (Judge Bao), Xīshī (a historical person), Mèngchángjūn (a historical person)
Geographical names of China: Běijīng Shì (City of Beijing), Héběi Shěng (Province of Hebei), Yālù Jiāng (Yalu River), Tài Shān (Mt. Taishan), Dòngtíng Hú (Lake Donting), Táiwān Hǎixiá (Taiwan strait)
Non-Chinese names translated back from Chinese will be written by their original writing: Marx, Einstein, London, Tokyo
Verbs (dòngcí): Verbs and their suffixes (-zhe, -le and -guo) are written as one: kànzhe/kànle/kànguo (to see/saw/seen), jìngxíngzhe (to implement). Le as it appears in the end of a sentence is separated though: Huǒchē dào le (The train [has] arrived).
Verbs and their objects are separated: kàn xìn (read a letter), chī yú (eat fish), kāi wánxiào (to be kidding).
If verbs and their complements are each monosyllabic, they are written together, if not, separated: gǎohuài ("to make broken"), dǎsǐ (hit to death), huàwéi ("to become damp"), zhěnglǐ hǎo (to straighten out), gǎixiě wéi (rewrite a screenplay)
Adjectives (xíngróngcí): A monosyllabic adjective and its reduplication are written as one: mēngmēnglìang (dim), lìangtāngtāng (shining bright)
Complements of size or degree (as xiē, yīxiē, diǎnr, yīdiǎnr) are written separated: dà xiē (a little bigger), kuài yīdiānr (a bit faster)
Pronouns (dàicí)
The plural suffix -men directly follows up: wǒmen (we), tāmen (they)
The demonstrative pronoun zhè (this), nà (that) and the question pronoun nǎ (which) are separated: zhè rén (this person), nà cì huìyì (that meeting), nǎ zhāng bàozhǐ (which newspaper)
Exceptions are: nàli (there), zhèbian (over here), zhège (this piece), zhème (so), zhèmeyàng (that way)... and similar ones.
Numerals and measure words (shùcí hé liàngcí)
Words like gè/měi (every, each), mǒu (any), běn (that), gāi (that), wǒ (mine, our), are separated from the measure words following them: gè guó (every nation), gè gè (everyone), měi nián (every year), mǒu gōngchǎng (a certain factory), wǒ xiào (our school).
