  Recently a population of compact radio galaxies were classified as
Fanaroff-Riley type 0 radio galaxies (FR 0s). The physical nature of FR 0s and
the connection with the classical FR I and II galaxies are not currently well
understood. Here, we report the radio properties of fourteen FR 0s on parsec
(pc) scales derived from their very long baseline interferometry (VLBI) imaging
observations. All sources show compact structures. Four sources show
relativistic beaming with Doppler boosting factors ranging from 1.7 to 6. The
brightness temperatures of the other ten are below the equilibrium limit. Jet
proper motions are determined in two sources which have multiple epoch data,
between 0.23 c and 0.49 c, implying mildly relativistic jet flow. Low-amplitude
flux density variation is found in J0943+3614 over a time period of 10 years.
No significant variability are detected in three other sources over time scales
of a few years. The radio properties of the FR 0s inferred from the VLBI data
resemble GHz-peaked spectrum or compact steep-spectrum sources. Moreover, the
diversity of their relativistic beaming indicators (brightness temperature,
variability, jet proper motion) also imply that FR 0s might not be a
homogeneous population of radio sources. Detailed studies of the low-power FR 0
sources in the local Universe additionally offer a promising opportunity to
understand their connection to the FR Is.
