Official dictionary of the U.S. judiciary system?
<p>Someone recently mentioned the "plain meaning" rule in one of my questions about statutory interpretation. Is there an official dictionary - like Merriam-Webster - that judges are supposed to rely on? Or do we assume that any of the leading publishers of dictionaries have essentially identical definitions?</p>

<p>I don't believe there is a single "standard" dictionary that judges use. Presumably any well regarded and common one will do as long as it can be cited. You can see from Justice Alito's opinion in <a href="https://www.supremecourt.gov/opinions/19pdf/18-1116_h3cj.pdf" rel="noreferrer">Intel Investment Policy Comm vs Sulyma</a> that he references several dictionaries. </p>

<blockquote>
  <p>Although ERISA does not define the phrase “actual knowledge,” its
  meaning is plain.  Dictionaries are hardly necessary to confirm the
  point, but they do.  When Congress passed ERISA, the word “actual”
  meant what it means to-day:  “existing  in  fact  or  reality.”  Webster’s  Seventh  New  Collegiate Dictionary 10 (1967); accord,
  Merriam-Webster’s Collegiate  Dictionary  13  (11th  ed.  2005) 
  (same);  see  also American  Heritage  Dictionary  14  (1973)  (“In 
  existence;real; factual”); id., at 18 (5th ed. 2011) (“Existing in
  reality and not potential, possible, simulated, or false”).  So did
  the word “knowledge,” which meant and still means “the fact or
  condition of being aware of something.”  Webster’s Seventh New 
  Collegiate  Dictionary  469  (1967);  accord,  Merriam-Webster’s
  Collegiate Dictionary 691 (2005) (same); see also American  Heritage 
  Dictionary  725  (1973)  (“Familiarity,  awareness, or understanding
  gained through experience or study”); id.,  at  973  (2011)  (same).<br>
  Thus,  to  have  “actual  knowledge”  of  a  piece  of  information, 
  one  must  in  fact  be  aware of it. Legal  dictionaries  give 
  “actual  knowledge”  the  same  meaning:  “[r]eal  knowledge  as 
  distinguished  from  presumed  knowledge  or  knowledge  imputed  to 
  one.”    Ballentine’s Law Dictionary 24 (3d ed. 1969); accord,
  Black’s Law Dictionary    1043    (11th    ed.    2019) (defining  “actual    knowledge”  as  “[d]irect  and  clear  knowledge,  as 
  distinguished from constructive knowledge”).</p>
</blockquote>

statutes interpretation