For one-word Jain naam jaap, the safest and most traditional options (accepted in both Digambar and Shwetambar parampara) are:

1. “Arihant”

- Arth: Remembering and bowing to the Arihant Bhagwan – the living, omniscient, passionless conqueror of inner enemies (krodh, maan, māyā, lobh). - Bhav: While repeating “Arihant, Arihant…”, think, “May I also walk towards such purity and vitarāgta.”

1. “Siddha”

- Arth: Remembering the Siddha Bhagwan – completely liberated souls, free from birth, death and all karmas. - Bhav: “May my soul also become pure like the Siddhas, free from all karma.”

1. “Navkar” (as a short name for Namokar Mantra)

- Some people softly repeat just “Navkar, Navkar…” as a reminder of the full Namokar Mantra, which bows to the Panch Parmeshti.

How to do one-word jaap (very simple way):

• Sit calmly, spine straight, eyes gently closed.
• Breathe naturally and repeat the chosen word slowly:

- “Arihant… Arihant…” or - “Siddha… Siddha…”

• Keep focus on the gun (virtues) of that Pad (Arihant/Siddha), not on worldly wishes.
• Start with a few minutes daily and increase as you feel comfortable.

All this is fully in line with Jain dharma because:

• You are not asking for material favors.
• You are remembering pure souls and their qualities, which helps in shuddhi of bhav and weakening of karmas.

For a fuller, multi-word jap, the primary and most powerful mantra remains the Navkar (Namokar) Mantra. You can read more here