If you need a free translation service that keeps terminology consistent across multiple translations, Omni is a good option. This tool is geared specifically for Asian novels, but it offers consistent and customizable terminology and can automatically detect terminology in linked translations. It's got a free Starter plan, but you can upgrade to a paid Pro plan for more features.
Another option worth considering is Crowdin, an AI-powered localization management service. It can handle continuous localization and multichannel translation for software, mobile apps, websites and other content. Its free plan only accommodates 60,000 words of hosted content, but it's a good option for agile teams that want to streamline and automate their translation workflow.
If you want a more mature online translation service, Reverso is a good option. It supports 15 languages and offers AI-based grammar and spell checking, neural machine translation and text translation. It can translate Word and PDF documents, too, so it's good if you need to keep terminology consistent across different documents.
Last, DeepL offers translations that are accurate and sound natural in many languages. It can translate text, documents and websites, so it's good for personal and professional use. It's got limited free use, but it can be useful for keeping terminology consistent if you're using it for broader purposes.