First, come what inflation actually is. Suppose in past you had to spend 100 USD for your daily necessity, but the same thing you have to cost more than 100 USD now, that means inflation is occurring. another example, in the previous you took a service for 100 USD cost, but at present same service spent you more than 100 USD, means inflation occurred.
This is definitely not that simple. All those you mentioned apply if the demanding and every other determinant for that service/product remain the same. You could define it shortly and more properly that way: Your salary remains the same and the total monetary units increase; thus, your purchasing power decreases.