Yajnya is the science of purification of the atmosphere through the agency of fire given through Vedas. The ancientmost body of knowledge known to humankind. This science is now presented as HOMA Therapy.
HOMA is synonym of Yajnya. All this knowledge was given in a language called Sanskrit which was nobody’s mother tongue at any time on earth. All languages of the world have words coming from Sanskrit. Sanskrit does not have a single word coming from other languages. Sanskrit has all the vocabulary required by modern technology and technology yet to come. Sanskrit is the language of interplanetary communication.
AGNIHOTRA, tuned to the biorhythm of sunrise/sunset is the basic YAJNYA which any person can perform with only a little effort.
There are Yajnyas to be done at the juncture of two seasons when there is a climate change. There are medicinal Yajnyas. There are some special Yajnyas to be performed based on astronomic conditions. These fall in the category Maha Yajnyas (Great Yajnyas). Somayag (Soma Yajnya) is one such Maha Yajnya.