The task of defining what constitutes a "word" involves determining where one word ends and another word begins—in other words, identifying word boundaries. There are several ways to determine where the word boundaries of spoken language should be placed:

Potential pause: A speaker is told to repeat a given sentence slowly, allowing for pauses. The speaker will tend to insert pauses at the word boundaries. However, this method is not foolproof: the speaker could easily break up polysyllabic words, or fail to separate two or more closely related words. Indivisibility: A speaker is told to say a sentence out loud, and then is told to say the sentence again with extra words added to it. Thus, I have lived in this village for ten years might become My family and I have lived in this little village for about ten or so years. These extra words will tend to be added in the word boundaries of the original sentence. However, some languages have infixes, which are put inside a word. Similarly, some have separable affixes; in the German sentence "Ich komme gut zu Hause an", the verb ankommen is separated. Phonetic boundaries: Some languages have particular rules of pronunciation that make it easy to spot where a word boundary should be. For example, in a language that regularly stresses the last syllable of a word, a word boundary is likely to fall after each stressed syllable. Another example can be seen in a language that has vowel harmony (like Turkish):[5] the vowels within a given word share the same quality, so a word boundary is likely to occur whenever the vowel quality changes. Nevertheless, not all languages have such convenient phonetic rules, and even those that do present the occasional exceptions. Orthographic boundaries: See below.

Orthography

In languages with a literary tradition, there is interrelation between orthography and the question of what is considered a single word. Word separators (typically spaces) are common in modern orthography of languages using alphabetic scripts, but these are (excepting isolated precedents) a relatively modern development (see also history of writing).

In English orthography, compound expressions may contain spaces. For example, ice cream, air raid shelter and get up each are generally considered to consist of more than one word (as each of the components are free forms, with the possible exception of get).

Not all languages delimit words expressly. Mandarin Chinese is a very analytic language (with few inflectional affixes), making it unnecessary to delimit words orthographically. However, there are a great number of multiple morpheme compounds in Chinese in addition to a variety of bound morphemes that make it difficult to clearly determine what constitutes a word.

Sometimes, languages which are extremely close grammatically will consider the same order of words in different ways. For example, reflexive verbs in the French infinitive are separate from their respective particle – e.g. se laver ("to wash oneself"), in Portuguese they are hyphenated – lavar-se, while in Spanish they are joined – lavarse.[6]

Japanese uses orthographic cues to delimit words such as switching between kanji (Chinese characters) and the two kana syllabaries. This is a fairly soft rule, as content words can also be written in hiragana for effect (though if done extensively spaces are typically added to maintain legibility).

Vietnamese orthography, although using the Latin alphabet, delimits monosyllabic morphemes rather than words.

In character encoding, word segmentation depends on which characters are defined as word dividers.