Ratha is a term for the spoked-wheel chariot used in Vedic literature (Bryant 2001). It has cognates in the Indo-Iranian, Italic, Celtic, Baltic and Germanic. The terms for the wagon pole, harness, yoke and wheel nave too have cognates in Indo-European.
Moreover, the whole idea of nomads with horse-drawn chariots has been challenged. Chariots are not the vehicles of nomads. Their usage occured only in ancient urban cultures with much flat land, of which the river plain of north India was the most suitable. Chariots are totally unsuitable for crossing mountains and deserts, as the proposed Aryan invasion required.
The rigvedic chariot is made of Salmali (RV 10.85.20), Khadira and simsapa (RV 3.53.19) and other woods native to India.Kazanas, Nicholas. 2001. The AIT and Scholarship
In RV 6.61.13, the Sarasvati river is described as being big like a chariot. Measurements for the chariot are found in the Sulba Sutras. The number of wheels of the Rigvedic chariot varies.
A similar term in the Rigveda is Anas ("cart"). The difference between Ratha and Anas is not clear.Kazanas, Nicholas. 2001. The AIT and Scholarship