primaryinfluence

noun
UK /ˈpraɪməri ˈɪnfluəns/
US /ˈpraɪmɛri ˈɪnfluəns/

The main thing or person that changes how someone thinks or acts.

Her grandmother was the primary influence on her love of cooking.


OTHER MEANINGS

2. The most important factor that causes something to happen.

Rainfall is the primary influence on crop growth in this region.

3. The strongest force shaping a person's early development.

His primary influence during childhood was his older brother.

4. The main source of change in a system or process.

Temperature is the primary influence on the reaction rate.