Throughout means in every part of something, or from start to finish. Throughout the country, throughout the day, throughout her life.
It works for space and for time equally, and that double duty is what makes it useful. It also stands alone as an adverb: the house was carpeted throughout. Compared with during, throughout insists on the whole span rather than some point inside it — during the meeting means at some moment in it, and throughout the meeting means the entire time. Note that it is always one word.
1prepositionthroughoutIn every part of, or for the whole time of.
“The same rule applies throughout the building.”
2adverbwholeIn every part; the whole time.
“The house has been rewired throughout.”
Too few real examples of this word to estimate which sense is commonest.
throughout is an extent in space or time.
The word is simply through plus out, joined in Old English. English built a small family this way — throughout, thereupon, whereby — and this is one of the few that stayed in everyday use.
Old English
þurh
English, today
throughout
From Old English þurh ūt, equivalent to through + out. Compare German durchaus (“all the way, fully, absolutely”).
Etymology from Wiktionary, CC BY-SA