As a measure against flooding, we piled up sandbags around our house.

Pisonia umbellifera, also known as Udonoki, is a plant commonly seen in tropical regions.

The Pisonia umbellifera is known for its beautiful flowers.

Mr. Takadono is my best friend.

The Fibonacci sequence appears in many phenomena in nature.

Solving problems of arithmetic sequence is difficult.

Understanding geometric sequences is important for understanding mathematics.

He is good at solving problems related to geometric sequences.

The chord progression of this song is very unique.

The speed of this progressive wave is close to the speed of light.