Radio-loud compact radio sources (CRSs) are characterised by morphological compactness of the jet structure centred on the active nucleus of the galaxy. Most of the local elliptical galaxies are found to host a CRS with nuclear luminosities lower than those of typical quasars, \(\lesssim 10^{42}\, \text{erg}\, \text{s}^{-1}\). Recently, low-luminosity CRSs with a LINER-like optical spectrum have been named Fanaroff–Riley (FR) type 0 to highlight their lack of substantially extended radio emission at kpc scales, in contrast with the other Fanaroff–Riley classes, full-fledged FR Is and FR II radio galaxies. FR 0s are the most abundant class of radio galaxies in the local Universe, and characterised by a higher core dominance, poorer Mpc-scale environment and smaller (sub-kpc scale, if resolved) jets than FR Is. However, FR 0s share similar host and nuclear properties with FR Is. A different accretion–ejection paradigm from that in place in FR Is is invoked to account for the parsec-scale FR 0 jets. This review revises the state-of-the-art knowledge about FR 0s, their nature, and which open issues the next generation of radio telescopes can solve in this context.

无线电响紧凑射电源（CRS）的特点是以星系活动核为中心的喷流结构的形态紧凑性。大多数本地椭圆星系被发现拥有核光度低于典型类星体的 CRS， \(\lesssim 10^{42}\, \text{erg}\, \text{s}^{-1} \) 。最近，具有类似 LINER 光谱的低光度 CRS 被命名为 Fanaroff-Riley (FR) 0 型，以强调它们在 kpc 尺度上缺乏大量扩展的无线电发射，与其他 Fanaroff-Riley 类相比，成熟的FR Is 和 FR II 射电星系。 FR 0 是当地宇宙中最丰富的一类射电星系，其特征是比 FR Is 具有更高的核心优势、更差的 Mpc 尺度环境和更小的（亚 kpc 尺度，如果已解析）喷流。然而，FR 0 与 FR Is 具有相似的宿主和核特性。调用与 FR Is 中不同的吸积-抛射范式来解释秒差距尺度的 FR 0 喷流。这篇综述修订了有关 FR 0 的最新知识、其性质以及下一代射电望远镜在此背景下可以解决的未决问题。