This activity will help your child develop an understanding of one whole and the parts that make up one whole. Try to use the language that is highlighted in the steps below since these are key words that your child will be hearing and speaking in school.
By using real world materials with your math activities you reinforce the concept of math being all around us.
Step  You and your child 
Buy a pie (or pizza or cake) and
introduce the word whole. 
"This is one whole pie. We are going to cut it in half first." 
Cut
the pie in half. 
"Now we have two halves." "Let's push them back together." 
Put the pie together again. 
"What do we have now?" "One whole." "Good." 
Take apart again 
"This is one half and this is one half. Two halves equal one whole." 
Cut the pie into four pieces. 
"Now we have four quarters. Four quarters equals one whole." "What if we take two of the quarters and put them back together, how many halves would we get?"

Take two of the quarters and
put them back together. 
"How many halves do we get?" "One." "Two quarters equals to one
half." 
Build on this activity  Have pizza for dinner and cake too (with a large dose of exercise as well!). As your child builds his or her word bank of fractions, continue to cut the food into smaller fractions. e.g. sixths and tenths. Draw attention to how the pieces are getting smaller. Note: Check with your child's school and teachers about whether the term "quarters" or "fourths" are used since different parts of the world use different terminology. 
The above math activity was created by Diane Massie, a HelpingWithMath.com contributor. It is part of her Handling Math program.
First hand experiences brings mastery of a skill and concept.