|Syntax and mark-up / Organisation of DITA elements|
Most DITA topic semantic elements can be categorised as block or phrase elements.
Block elements are paragraph-like elements that are typically displayed in the output with space above and below the content, taking up the full width of the available space. Phrase (or inline) elements are applied to words or phrases within a block element, and typically do not force new lines in the output.
Block elements can exist within other block elements, but not within phrase elements.
Phrase elements can exist within block elements and within other phrase elements.