This is the 263rd most frequent Arabic word.
كانوا
"They were."
The word "كانوا" here indicates the past continuous tense they verb "to be" in third-person plural form.
كانوا يعملون بجد طوال الأسبوع.
They were working hard all week.
"كانوا" is used to indicate a state or condition in the past for the plural entity.
كانوا في المنزل عندما هطل المطر.
They were at home when it rained.
In this context, "كانوا" is used to suggest a hypothetical or intended action in the past for the plural.