momentary

"He measured his success relatively, that is, competitively."

"The student had a perpetual smile, always seeming happy. "

"Let me tell you how it happened."

"The candle flickered in the breeze, almost going out. "

"The beauty of cherry blossoms is ephemeral, lasting only a week or two each spring. "

"The darkness of the room made it difficult to see."

"He is a student of life."

"My concentration was high during the important math test. "

"The new software is a generator of innovative ideas for students' projects. "

"The volunteers are lasting through the marathon, carrying out the task of supporting the runners. "

"The crowd was distracted by a helicopter hovering over the stadium when the only goal of the game was scored."

"The lightning caused thunder."