See my answer above. Depending on the context it may or may not need to be translated. If Duo gives English words with which you can only make up 'the Senedd' than go with that ('the Senedd' is the name of the Assembly building in Cardiff), if it gives you either 'senate' or 'parliament' then use that.
- senedd = a senate; a parliament
- Y Senedd = the Senedd (in the Welsh context where that is the name of the building in Cardiff Bay where the Welsh Assembly sits - http://www.assembly.wales/en/visiting/senedd/Pages/Senedd.aspx - click on the Cymraeg button to read the Welsh-language version)
This is one of the Welsh words, like Eisteddfod, that are not translated but are used in both English and Welsh. In a similar way to the Irish parliament 'Dáil' and Irish prime minister 'Taoiseach'.
Senedd is also used to describe 'Senate' or upper house in bicameral legislatures or parliaments, in particular the Senate of the USA.
The Welsh government is a unicameral (single chamber) devolved administration and so 'Senedd' corresponds to parliament, which is one of the accepted alternative translations here.