Scriptio continua ("Continuous script" in Latin; also scriptura continua) is a style of writing without spaces or other marks between words or sentences.
In the West, the oldest Greek and Latin inscriptions use word dividers, but these are rare in the later periods when scriptio continua becomes the norm (in Classical Greek and late Classical Latin). By around 1000 AD, alphabetical texts in Europe are written with spaces between words. Scriptio continua is still in use in Thai, other Southeast Asian abugidas, and in languages that use Chinese characters (Chinese and Japanese) though with sentence breaks. Modern Chinese differs from ancient scriptio continua in that it does at least use punctuation, although this was borrowed from the West only about a century ago. Before this, the only forms of punctuation found in Chinese writings were punctuations to denote quotes, proper nouns, and emphasis.
Before the advent of the codex (book), Latin and Greek script was written on scrolls. Reading continuous script on a scroll was more akin to reading a musical score than reading text. The reader would typically already have memorized the text through an instructor, had memorized where the breaks were, and the reader almost always read aloud, usually to an audience in a kind of reading performance, using the text as a cue sheet. Organizing the text to make it more rapidly ingested (through punctuation) was not needed and eventually the current system of rapid silent reading for information replaced the older slower performance declaimed aloud for dramatic effect.