The following terms are developed and/or defined in this grade level's materials.

ADD AND SUBTRACTION RELATION  EVEN AND ODD NUMBER  PLACE VALUE 
ADD BY REGROUPING  FOOT (MEASUREMENT)  PROBLEM SOLVING 
ADDEND (WHOLE)  IDENTITY (ADDITION)  TIME 
BAR GRAPH  INEQUALITY SIGN  VERTICES (SOLIDS) 
  
  
  
  
  
The following terms appear in this grade level's materials. At this grade level the terms are used in the lesson proper in examples or illustrations.
The purpose here is to reinforce understanding of the terms.

ADD BY NUMBER LINE  EQUATION  RECTANGULAR PRISM 
ADDITION (WHOLE)  FACE (POLYHEDRON)  REPEATED ADDITION 
ANGLE  FREQUENCY TABLE  RULER 
CENTER (CIRCLE)  HEXAGON  SHAPE 
CENTIMETER  INCH  SPHERE 
CIRCLE  LENGTH  SQUARE 
COLLECTING  MEASUREMENT  SUBT. (TWO PLACE) 
COLUMN ADDITION  MEASUREMENT (LENGTH  SUBTRACTION 
COMMUTATIVE (ADD.)  MONEY  SYMBOLS FOR ADDITION 
COMPARISON  MULTIPLICATION (WHOLE)  SYMBOLS FOR MULTIPLICATION. 
COMPASS  NUMBER SENTENCE  TABLES 
CONE  ONE HALF  THREE ADDENDS 
COUNTING  ORDINAL NUMBER  THREE DIMENSION 
CUBE  PENTAGON  TRIANGLE 
CYLINDER  POINT  TRUE AND FALSE 
DIVISION (WHOLE)  QUADRILATERAL  WRITING NUMBERS 
EDGE (POLYHEDRON)  RECTANGLE  
  
  
  
  
  
A synonym of the following terms are used. The synonym helps to bridge the learner's non mathematical experiences to mathematics terms that will more formally be worked on.
A synonym may also be used because these historical terms may have been replaced by a new vocabulary (k12math.info's list of 1,000 terms has not changed in 40 years).
Wiktionary dictonary may help here.

ADD. COMBINATIONS (WHOLE)  INEQUALITY  MULTIPLES OF TWO 
APPROXIMATION  INTERPRETATION  PICTOGRAPH 
EQUALITY  MULTIPLES OF TEN  WORD PROBLEMS (WHOLE) 
ESTIMATING SUMS   
  

K12math.info selected the content that appears here. All terms appear in the lesson proper. The selection process is based upon a content analysis of 2013 to advance copies of 2015 student mathematics
textbook series. Series that base their content on 2010 and/or 2012 standards. The analysis also included content that was felt would be needed for the
transistion to CK12 existing textbook series.
Editor's Note: This is a very basic outline of the content and how they are to be developed in the lesson proper. These terms need to be used in examples, illustrations, class activities and homework to help further understand them.
Resources:
Learners age 5 to 11 Grades K through 6 (from Wikieducator's "Come fly with me..." project).
Key points in Writing a textbook. (Especially step 7)
Teaching OER Mathematics.
Learning design a Wikieducator.org project.
Additional observations made while collecting information for this site on unit development in a textbook:
 One type has a chapter unit divided into 3 parts:
Part 1 has a written explanation of the concept being developed (or defined).
Part 2 has examples and illustrations of the concept.
Part 3 classroom and/or homework activities.
 Another approach consists of 2 parts:
Part 1: the concept being developed (or defined) is being used in several carefully designed examples and illustrations.
Part 2: classroom and/or homework activities.
