What are frequencies?

Some articles on frequencies:

Soundbox
... or resonant behavior, that is, it naturally oscillates at some frequencies, called its resonant frequencies, with greater amplitude than at others ... Resonators are used to either generate waves of specific frequencies or to select specific frequencies from a signal ...
Grupo Aeroportuario Del Pacífico - Statistics
... This is due to the decrease of routes and frequencies by many airlines ... compared to March 2008, for a total of 971 frequencies and a total of 63 routes operated by these types of carriers ... The decline in frequencies was mainly due to a restructuring of routes and frequencies by the airlines, with the objective of increasing profitability as a result of the ...
HLA-B*82 - Serotype - Allele Frequencies
... HLA B*8201 frequencies freq ref. 0.3 Kenya 0.3 Kampala (Uganda) 0.3 Nandi (Kenya) 0.2 ' HLA B**8202 frequencies Sudanese 2.5 Kenya 0.7 Guraiat and Hail (Saudi Arabia) 0.2 ...
HLA-B46 - B*4601 Allele Frequencies - A2-Cw11(1)-B46
... This event happened recently as there is only one major allele and minor alleles are at trace frequencies ... peoples have traveled and is found at low frequencies in non-farming indigenous groups ... HLA A2-B46 haplotype frequencies freq Rank in ref ...