Vinayagar has many names and many forms of His own. 

The word Vinayagar or Vinayagan is a combination of Vi + Nayagan."Vi" means "No" while "Nayagan" means "head". Vinayagar literally means He who has no leader. That is, He himself is the leader of all and therefore the highest.

Ganapati = gana + pati.Pati = Lord; gana = Siva's warrior attendants. Therefore it means the Lord of Siva's warrior attendants.

Ganapati also has another meaning derived from the root words ga + na + pati. Ga = going (into the world of knowledge); Na = the end (of this knowledge); and Pati = Lord.Therefore the Lord of both the path and goal/end and therefore the highest.

Ganesan = easan + gana. Easen = Lord. So Lord of Siva's attendants.

Vigneswaran = vigh + easwaran.Vigh = obstacles; Easwaran = Lord. Therefore it means Lord of obstacles and Remover of obstacles.

Siddhivinayagar/Sithivinayagar = siddhi + vinayagar. Siddhi = powers or fulfillment; vinayagar = the top leader. This name therefore means the leader who confers powers or fulfillment on devotees.

Gajamugha = gaja + mugham.Gaja = elephant; Mugham = face. It means the elephant-faced One. Gajananan carries the same