This is the 673rd most frequent Ukrainian word.
об
The Ukrainian word "об" means "about" or "concerning."
In this case, "об" introduces a subordinate clause beginning with "тому," where it emphasizes the subject of the talk, creating a smooth transition.
Він говорив об тому, як важливо допомагати іншим.
He talked about the importance of helping others.
The usage of "об" precedes the noun "умовах" to convey the subject of agreement clearly, following phonetic rules for clarity and flow.
Ми домовилися об умовах співпраці.
We agreed on the terms of cooperation.
Here, "об" is used before "безпеці" to facilitate the flow in the preposition-noun combination, due to phonetic rules where "об" is preferred over "о" before certain sounds for easier articulation.