1. Decide; determine; decree.

2. (obsolete, transitive) Decide; determine (a matter disputed or doubtful).

3. with infinitive or object clause

4. intransitive

5. (transitive) Decree by judicial sentence. Now a technical term of Scottish judicature; the use of the word decerns being necessary to constitute a decree.

6. with simple object

7. Decree by judicial sentence that something be done.

8. Decree a person etc. to be or to do something by judicial sentence.  (in the phrase “to decern in”, obsolete) To mulct in by decree of court.

9. transferred sense

10. Discern.

11. (obsolete, transitive) Distinguish or separate by their differences (things that differ, one thing from another).

12. (intransitive) Distinguish; discriminate between.

13. See distinctly (with the eyes or the mind); distinguish (an object or fact); discern.