This is the 8269th most frequent Japanese word.
康男
"康男" is a Japanese male given name, typically meaning "Healthy/Gentle Man."
Here, 康男 is used as a proper noun to name a person in a formal context by appending the respectful "さん".
康男さんは大学で経済学を専攻しています。
Yasuo studies economics at university.
In this sentence, 康男 is used as a personal name without a suffix, suitable for contexts where the speaker has familiarity with the individual.
康男が昨日の会議で発言した内容は重要でした。
The points Yasuo made during yesterday's meeting were important.
Here, 康男 identifies the name of the speaker's best friend, serving as the primary subject of the sentence.