In certain types of compound inflorescence: a subsidiary branch that has the same branching structure as the main axis.
1960s. From German Parakladium (W. Troll InfloreszenzenI.ii. i; earlier, in slightly wider sense, C. H. Schultz Neues System der Morphologie der Pflanzen i. 4) from para- + ancient Greek κλάδος branch + scientific Latin -ium.