We analyze several approaches to the thermodynamics of tachyon matter .
The energy spectrum of tachyons \varepsilon _ { k } = \sqrt { k ^ { 2 } - m ^ { 2 } } is defined at k \geq m and it is not evident how to determine the tachyonic distribution function and calculate its thermodynamical parameters .
Integrations within the range k \in \left ( m, \infty \right ) yields no imaginary quantities and tachyonic thermodynamical functions at zero temperature satisfy the third law of thermodynamics .
It is due to an anomalous term added to the pressure .
This approach seems to be correct , however , exact analysis shows that the entropy may become negative at finite temperature .
The only right choice is to perform integration within the range k \in \left ( 0 , \infty \right ) , taking extended distribution function f _ { \varepsilon } = 1 and the energy spectrum \varepsilon _ { k } = 0 when k < m .
No imaginary quantity appears and the entropy reveals good behavior .
The anomalous pressure of tachyons vanishes but this concept may play very important role in the thermodynamics of other forms of exotic matter .