Daleth = 4, ordinal 4, reduced 4, no final form. Spelled in full, דלת = 4+30+400 = 434.
Meaning
Daleth is 'door' and one of the seven doubles (d/dh). The Talmud's homily reads it as the poor man (dal) at the door, paired with gimel's rich man, so that the two letters are a single sentence about charity. Its 4 is the number of the elements and of the four worlds, and on the tree it is the door between the two supernals.