This is the 5679th most frequent Japanese word.
せいこう
Success.
In this case, "成功" (せいこう) is used as a noun meaning "success." It signifies the completion or achievement of a goal.
彼はプロジェクトの成功を祝った。
He celebrated the success of the project.
Here, "成功する" (せいこうする) is used as a verb meaning "to succeed." It pertains to the act of achieving success.
その方法を使えば成功する可能性が高い。
Using that method has a high chance of succeeding.
Again, "成功" (せいこう) is used as a noun, emphasizing the concept of success as an outcome or state.