S wave
The abbreviation often used for secondary waves is S-waves.
primary and secondary waves
Infrared waves.
Electromagnetic waves.
ultrasonic waves
Radio waves at the frequency of 2,450 MHz, often inaccurately referred to as "microwaves".
primary and secondary waves
The abbreviation often used in Freemasonry is Stwd.
Primary (P) and Secondary (S) waves
Infrared waves.
Ca is often used as a medical abbreviation for cancer.
The abbreviation for township is TWP. This abbreviation is often used on road signs and some official documents abbreviate it as TWSP.
Primary waves are called so because they are the first to arrive, and secondary waves are called so because they arrive second. Based on this logic I would say no. There is in fact a marked difference, which is used to tell how far away the epicenter is from a particular seismograph.
A personal computer is commonly known by the abbreviation P.C.
CT is often used as the abbreviation for Chlamydia trachomatis, the bacteria that causes chlamydia.
jk is and abbreviation often used in texting for just kidding
An epitaph
Cos. is the plural, but more often used is the abbreviation for the word company instead which is Co.