• 永久えいきゅう — permanent / everlasting
• 久ひさしぶり — after a long time
• 久ひさしい — long time (has passed)
• 久々ひさびさ — for the first time in a while
• 久保くぼ — common surname

久 is an ancient character that represents “a long period of time.” It originates from the image of stretching or pulling. In cursive script, it resembles the shape of “く,” and is considered one of the roots of the hiragana character.