The rules for visibility in 5e were a mess. The rules in One D&D appear to continue being a mess. As far as I can tell the intended rule is:

1. See is a term of art that Usually but not always means vision. This is a cause of a great deal of confusion.
2. Blindness means you cannot use vision. This means you cannot see unless you have another ability.
3. Blindsight is the ability to see without using vision.
4. Hidden, in 5e, means you are neither seen nor located. One D&D appears to have removed the second effect.
5. Invisibility means you cannot be seen with vision, unless you have a special ability (such as see invisibility or truesight) that allows doing so.
6. Located means enemies know your location. Senses such as hearing and tremorsense can locate but cannot see. In 5e, it is normally assumed that anyone who is not hidden is located; One D&D has not discussed this.
7. In 5e, attack rolls against unseen opponents are at disadvantage. One D&D has not discussed total concealment, but other forms of being unseen do this.
8. In 5e, attack rolls by unseen opponents have advantage. One D&D has not discussed total concealment, but other forms of being unseen do this.
9. In 5e, many spells can only affect targets you can see. From what they've said, this remains true in One D&D.
10. In 5e, you cannot make opportunity attacks against targets you cannot see. One D&D has not discussed this.

Any of these points might be wrong, but the actual question I'm curious about, which I don't have a good answer for, is:

How can this be expressed in a way that is clear, concise, and avoids unnatural constructions like "see without vision"?

A start for me would be something like

• Find a new term to replace see in spell descriptions. I have no good candidates.
• Find a new term to replace unseen.
• Unseen becomes a specific status. Unlike many status effects, it applies to a relationship (charmed and frightened already do similar things)
• Blindness means 'you cannot use vision to see. All creatures are unseen unless you can see in some other way'. Remove all other text.
• Blindsight means 'you can see with sense other than vision'.
• Invisible means 'creatures cannot use vision to see you, unless they have a specific ability that lets them do so'. Remove all other text.
• See Invisibility and Truesight allow you to use vision to see invisible creatures.

However, there may be a clearer way of writing this, and I would really like a replacement for seen/unseen. It might be nice to have vision be a range keyword (e.g. magic missile becomes 'Range: perception, max 120') to make it easier to see, as whether it requires vision is actually quite important for spells.

So... candidates? If you disagree with my interpretation of RAI, feel free to state what you think the the rules should be as well as your alternate wording.