Yagna (also known as Yajna, Yagya) is a ritual of sacrifice, practised during the Vedic age by the Hindus, to appease the Gods or the Supreme Spirit Brahmin. Yagna is the outer form of worship in which offerings are made to different deities in a systematic manner, to help the worshipper achieve certain results in life. The concept lays emphasis on the pouring oblations into the sacrificial fire, while reciting the mantras, so that it directly reaches the Gods.

The chanting of mantras is expected to ensure fulfillment of specific desires, the overall welfare of an individual, a group of people or the entire society. Yajna is used on most important occasions, ranging from weddings to the opening of new businesses to graduations to prayers for someone`s health. Some Yagnas are also performed on large scale for the general welfare of the entire community, to increase fertility of soil, to invite rains, to welcome peace and wealth etc.

Depending upon the degree of complexity, these yagnas may last from a few hours to several days. The number of priests participating and conducting the ceremony would depend upon the nature and objective for which it is performed. The outer aspect of Yajna consists of building an altar, generally with bricks, kindling fire using specific types of grass and wood. A Yajna is typically performed by a hotar, along with many additional priests chanting Vedic verses. Often there will be a fire in the centre of the Yajna and items are offered into the fire. The offering, which is placed into the fire, consists of several elements, including jav, sesame seeds, rice, ghee, incense and sandalwood. Each element has a different significance. This Yajna, where milk products (ghee or yogurt), fruits, flowers, cloth, and money are offered, is also termed homa or havan.

The Hindu tradition has the Pancha Mahayajnas (Five Great Yajnas) namely:
Devayajna- consists of offering ahutis to devas.
Pitruyajna- consists of offering libations to ancestors or pitrus.
Bhutayajna- consists of offering bali or foodstuffs to all creatures.
Manushyayajna- consists of feeding guests.
Brahmayajna- consists of chanting Vedas, namely Rig veda, Yajurveda, Samaveda and Atharva veda.

There are also the three kinds of Srauta Yajnas, which explicitly describe around 400 yajnas in the Vedas In the category of nitya- karma there are 21 sacrifices. There is no compulsion with regard to the rest of the 400 Yajnas. But the 21, included in the forty samskaras, are required to be performed at least once in a lifetime of a Dvija. These are divided into groups of seven - pakayajnas, havir-yajnas, and soma-yajnas. Let us understand all of them in detail.

The Pakayajnas are minor sacrifices and are performed at home. This is the simplest form of Yajna and a domestic ritual performed by the householder who would offer simple oblation into the sacred fire lit in his house. On every first day of the lunar fortnigh), a pakayajna and a haviryajna have to be performed in the grhyagni and shrautagni respectively. The first is called sthalipaka. "Sthali" is the pot in which rice is cooked and it must be placed on the aupasana fire and the rice called "caru" cooked in it must be offered in the same fire.

Haviryajnas are more elaborate, though not so large in scale as the somayajnas. The haviryajna performed on every Prathama is "darsa-purna-isti", "darsa" meaning the new moon and "purna" the full moon. So the "istis" or sacrifices conducted on the day following the new moon and the full moon (the two Prathamas) are together given the name of darsa-purna-isti. The two rituals are also referred to merely as "isti". This is the prakrti (archetype) for haviryajnas. The first four haviryajnas - adhana, agnihotra, darsa-purna-masa and agrayana - are performed at home. The last three haviryajnas - caturmasya, nirudhapasubandha and sautramani - are performed in a yagasala. The name Somayajna is derived from the fact that the essence of the Soma plant, said to be relished by the celestials, is made as an oblation. For soma sacrifices "agnistoma" is the prakrti, the word "stoma" also means a sacrifice. The Saman is sung. In such soma sacrifices there is the hotar, the adhvaryu, the udgatar and the brahma and every priest is assisted by three others. So in all there are sixteen priests in a soma sacrifice.

Agnistoma which is the first of the seven somayajnas is the prakrti (archetype) and the other six are its vikrti. These six are: Atyagnistoma, Uktya, Sodasi, Vajapeya, Atiratra and Aptoryama. Vajapeya is regarded as particularly important. When the worshipper comes after having had his ritual bath at the conclusion of the sacrifice, the king himself holds up a white umbrella for him. "Vaja" means rice (food) and "peya" means a drink. As the name suggests, the vajapeya sacrifice is believed to bring in a bountiful crop and plentiful water. This sacrifice consists of soma-rasa homa, pasu-homa (23 animals) and anna - or vaja-homa. The sacrificer is "bathed" in the rice that is left over. Since the rice is "poured over" him like water the term "vajapeya" is apt.

It is a fact that the incidence of performing the yagnas and other forms of sacrifices is slowly deteriorating in modern Hindu Society. Hence, today many educated Hindus are not very serious about performing the yagnas and for most of them they are just a part of the tradition, without any significance. The influence of western education, the complexity involved in performing the Yagnas and the decreasing number of priests are the main reasons for it. However, some devout Hindus still believe in their efficacy and organize Yagnas for various purposes, sometimes in public for a social cause or sometimes in private for a personal gain. Thus, there are yagnas for acquisition of a spouse, childbirth, wealth, removal of obstacles, family happiness, and so on.

For the purposes of ameliorating a difficult period or sub period, the nava graha or nine-planet yagna is usually recommended because it is both effective and reasonably affordable. If a person`s problems are too intense however, a bigger yoga, one lasting seven or eight days, may be necessary. It is preferable to be present with the priest during the Yagna, but the ceremony can also be performed in absence with fine results.