Notes
Lookup is a loosely coupled relationship, allowing you to connect one object to another in a one-to-many fashion.
- Lookup relationships are used when you want to create a link between two objects, but without the dependency on the parent object.
- Up to 40 allowed for object after summer 16 release.
- No impact on deletion.
- Lookup field is not required
You can have a Total of 40 Relationship fields with a Maximum of 2 Master Detail Relationships.
So you can have all 40 as Lookup Relationship fields,
38 Lookup and 2 MD
39 Lookup and 1 MD relationship fields on an object