What are some words with no singular form?

You're asking about uncountable nouns, also known as mass nouns. These are words that refer to things that cannot be easily counted or separated into individual units.

Here are some examples of uncountable nouns:

* Substances: water, air, sand, rice, furniture, music, information, advice, knowledge

* Concepts: happiness, love, anger, time, beauty, peace, progress

* Collections: luggage, equipment, machinery, jewelry, clothing, mail

* Abstract Ideas: research, evidence, research, homework, progress, work

Important Note: Some words can be both countable and uncountable depending on their context. For example:

* "I have three pieces of advice for you." (countable)

* "She gave me some good advice." (uncountable)

Let me know if you'd like to explore specific categories of uncountable nouns in more detail!