Read the following information carefully and answer the given questions.

Vedas, meaning "knowledge," were written in Vedic Sanskrit between 1500 and 500 BCE in the northwestern region the Indian Subcontinent. The Vedas were transmitted orally during the course of numerous subsequent generations before finally being archived in written form. Not much is known about the authors of the Vedas, as the focus is placed on the ideas found in Vedic tradition rather than those who originated the ideas. The oldest of the texts is the Rig Veda, and while it is not possible to establish precise dates for each of the ancient texts, it is believed the collection was completed by the end of the 2nd millennium BCE (Before Common Era).

There are four Indo-Aryan Vedas: the Rig Veda contains hymns about their mythology; the Sama Veda consists mainly of hymns about religious rituals; the Yajur Veda contains instructions for religious rituals; and the Atharva Veda consists of spells against enemies, sorcerers, and diseases. (Depending on the source consulted, these are spelled, for example, either Rig Veda or Rigveda.)

The Rig Veda is the largest and considered the most important of the collection, containing 1,028 hymns divided into 10 books called mandalas. The verses of the Sam Veda are taken almost completely from the Rig Veda, but arranged differently so they may be chanted. The Yajur Veda is divided into the White and Black halves and contains prose commentaries on how religious and sacrifices should be performed. The Atharva Veda includes charms and magic incantations written in the style of folklore.

Each Veda was further divided in two sections: the Brahmanas, instructions for religious rituals, and the Samhitas, mantras or hymns in praise of various deities. Modern linguists consider the metrical hymns of the Rigveda Samhita, the most ancient layer of text in the Vedas, to have been composed by many authors over several centuries of oral tradition. Although the focus of the Vedas is on the message rather than the messengers, such as Buddha or Jesus Christ in their respective religions, the Vedic religion still held gods in high regard.

The Aryan pantheon of gods is described in great detail in the Rig Veda. However, the religious practices and deities are not uniformly consistent in these sacred texts, probably because the Aryans themselves were not a homogenous group. While spreading through the Indian Subcontinent, it is probable that their initial religious beliefs and practices were shaped by the absorption of local religious traditions.

According to the hymns of the Rig Veda, the most important deities were Agni, the god of Fire, intermediary between the gods and humans; Indra, the god of Heavens and War, protector of the Aryans against their enemies; Surya, the Sun god; Vayu, the god of Wind; and Prthivi, the goddess of Earth.

What is the synonym of the word-'ancient' as used in the passage?