The growth that make plants thicker is called primary/secondary growth.

Explanation

To determine the type of growth that makes plants thicker, we need to understand the concepts of primary and secondary growth in plants.

### Step-by-Step Solution:

1. **Understanding Primary Growth**:
- Primary growth is defined as the growth that occurs at the tips of stems and roots due to cell division.
- This type of growth results in the elongation of the plant, meaning it increases in height or length but does not contribute to the thickness of the plant.

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