Here's why:
* "pH" is an abbreviation. Using an abbreviation at the beginning of a sentence feels jarring and informal.
* "pH" is a technical term. Starting a sentence with a technical term can make it sound overly academic or dry.
Instead of starting with "pH," consider rephrasing your sentence to put the subject first. Here are some examples:
Original: pH is a measure of acidity or alkalinity.
Revised: The pH of a solution measures its acidity or alkalinity.
Original: pH is important in many chemical reactions.
Revised: The pH level plays a crucial role in numerous chemical reactions.
However, there might be rare situations where starting a sentence with "pH" is acceptable, such as:
* In highly technical writing: If you're writing for a specific audience that is familiar with the term and the context is very technical, starting with "pH" might be acceptable.
* For emphasis: If you want to emphasize the importance of pH, you might choose to start with it for dramatic effect.
Ultimately, it's up to your discretion, but it's generally best to avoid starting sentences with "pH" unless it's absolutely necessary.