They climbed the mountain together, reaching the summit.
Meaning: This means to work together to achieve a difficult goal. It's like saying, They worked as a team to get to the top.
Choice of Words: Climbed is a verb that means to move upwards on a steep surface. Summit is a noun that means the highest point of a mountain. When you put them together, "climbed the mountain together, reaching the summit" means that they worked together to get to the top of the mountain.
Alternative Expressions
Related Expressions