A spontaneous process is also called a ...... process.

Explanation

To answer the question, "A spontaneous process is also called a ...... process," we can follow these steps:

### Step-by-Step Solution:

1. **Define Spontaneous Process**: A spontaneous process is one that occurs naturally without the need for external energy input. It happens on its own due to the inherent properties of the system.

2. **Identify Alternative Terms**: Spontaneous processes are often referred to by other terms. The most common alternative term is "natural process." Additionally, they can also be called "feasible processes" or "physical processes."

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