I have been a member for only months and this already drives me nuts!! A thermometer and a thermostat are very different devices!
Understanding terminology, semantics, acronyms and abbreviations is understandably a learning process for this hobby. Trying to get the message across about the difference and importance of two words that have different definitions/meanings gets frustrating. I applaud the veterans here who have the time and patience to go over it again and again.
A thermometer only reads the temperature. That is all it does, nothing else. It tells you temperature, like getting checked if you have a fever because you are sick.
A thermostat reads the temperature and makes sure it doesn't get too warm or too cold. The lever "thingy" on the wall you move because you are too cold or too warm in your house is a thermostat! It reads the temperature and you can adjust it.
There is not such thing as a hydrometer in herpetology! A hydrometer is most often used by a person making their own beer, wine and cider. Any other person using a hydrometer is getting paid for their biology/chemistry degree.
A HYGROmeter measures the humidity. A thermometer measures temperature. A thermostat measures temperature AND keeps a near constant temperature just like the thermostat in your home!
New and ignorant people need to remember this. Ignorant people need to remember that the definition of ignorant is a lack of knowledge. Reducing ignorance is reading and asking for clarification. I always say ignorance can be cured but never by being spoon fed.
There is a lot of knowledge and science involved in keeping reptiles. Treat it like a lifelong science experiment. Advice for concerns is only as good as the information BP.net members can read. Be very specific and don't worry about the length. Get the words right the first time. Use the search function because someone yesterday or last week, last month, last year asked something very similar. Good people are here but they get frustrated if/when others don't show a willingness to read and learn.