You can quickly look up words while working in applications such as Pages or Mail. You can also specify whether the definition appears in a small or large window.
To look up a word using the mouse:
In most applications, hold down the Control key as you click the word, and then choose “Look Up in Dictionary” from the shortcut menu.
In Pages, hold down the Control key as you click the word, and then choose Writing Tools > ”Look up in Dictionary and Thesaurus” from the shortcut menu.
To look up a word using the keyboard:
In most applications, place the pointer over the word you want to look up without clicking the word. Press Control-Command-D.
In Pages, select a word, and then press Control-Command-D.
To specify a small or large window:
Choose Dictionary > Preferences.
Click “Opens Dictionary application” to view definitions in the full Dictionary window, or “Opens Dictionary panel” to view them in a small window (panel).
In panel view, click More to view the complete entry in the full Dictionary window. To change the source, click the pop-up menu in the lower-left corner of the panel.