Size, materials, form, meaning and symbolism, or fashion and age are a few of the main ways necklaces can be differentiated.

1. Necklace Sizes, Meanings and
Symbolism
Necklaces are popular among all ages, cultures and gender. Necklaces
can be classified in many different ways and for different reasons. Size,
materials, form, meaning and symbolism, or fashion and age are a few of
the main ways necklaces can be differentiated.
Necklace Size Classifications
The most common types of size classifications are:

2. Necklace Meanings & Symbolism
This is probably the most diverse of all the categories, as it covers all
aspects of life. Over the ages, necklaces have been used as symbols for
everything from wealth and status to religious and spiritual icons
through to forms just for beauty and style.
A few of these include:

3. You might also like reading the following posts about DIY necklace:
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Sacred Cross Necklace from Zacoo
Source from:
http://www.beadset.com/necklace-sizes-meanings-and-symbolism/